Leaders of the noncommunist world's seven major industrial nations begin an economic summit conference in Ottawa tonight, and while high U.S. interest rates and Japanese exports are expected to be chief topics, the talks are being billed by most of the participants as largely a get-acquainted session.

Four of the leaders, including President Reagan, will be attending their first session of the annual conference, which began in 1975 in the depths of the economic chaos that followed the first major oil price increases.

Past conferences have produced few concrete results, and Canadian Prime Minister Pierre Elliott Trudeau, this year's host, has tried in the last few days to dampen expectations of any major decisions this year.

But the purpose of the talks, most participants say, is rather to give leaders of the countries that produce more than half the world's manufactured goods a chance to candidly educate one another about their problems, according to reports from Washington Post correspondents in the countries taking part.

Most of the three days of talks will be held at the secluded Chateau Montebello, a resort hotel in Quebec Province about 45 miles east of Ottawa, to give the leaders utmost privacy. The final talks Tuesday are scheduled in Ottawa's Parliament.

In addition to Reagan, those attending for the first time will be President Francois Mitterrand of France and Prime Ministers Zenko Suzuki of Japan and Giovanni Spadolini of Italy. Trudeau and West German Chancellor Helmut Schmidt are veteran participants, and British Prime Minister Margaret Thatcher attended last year's talks.

With dipolmatic tensions high on the issues of U.S. interest rates and Japanese exports, much effort may be devoted to avoiding disputes. Trudeau, at a press conference last week, said "I wouldn't be prepared to guarantee that there won't be some clash in private," but he added that any public expressions of conflict would come as a surprise to him.

Despite Thatcher's public truculence on many of the issues to be discused, Britain is known to by smpathetic to Trudeau's appeal to avoid open splits. Schmidt also is eager to avoid the appearance of a quarrel.

The Japanese have said privately that they prefer a rather vague and unfocused assemblage. "To expect a summit such as this to launch anything completely new and specific would be disturbing," one official involved in Japan's planning for the conference said. A foreign economist said in Tokyo, "The Japanese want to get through it with the least amount of trouble."

Discussion of political issues such as East-West relations, the Middle East, Central America and southern Africa is expected to be limited to tonight's opening dinner meeting, with Monday and Tuesday devoted to economic matters.

The conference has forced Canada to mount a vast security operation costing more than $1.5 million. Thousands of police officers have been assigned to the conference sites, and an antiterrorist squad of Royal Canadian Mounted Police has been trained by Britain. Canada has bought seven armor-plated cars at a reported cost of more than $70,000 for the leaders to use.

Washington Post correspondents filed the following reports: Canada

OTTAWA -- Trudeau, host of this year's economic summit, has recognized that opposition by France and other European nations to U.S. interest rate policy may hinder the quest for harmony at the conference.

Trudeau has been equivacal in spelling out his feelings on the policy. "We're trusting you but when do you think it's going to work?" was how he summed up the position he hopes summit participants will take in questioning Reagan.

As chairman, Trudeau has said he will seek a consensus that Reagan's economic policies should be respected. But there is no point in pretending that the high rates in the United States are not being felt elsewhere, he said.

Trudeau takes special interest in Third World problems, but he admitted Wednesday that he was unsure whether summit participants would commit themselves to greater efforts to promote Third World development.

Despite his recent visits to many of the summit participants to set the stage for a full discussion of North-South issues, Trudeau said he had "no firm commitment" from other leaders that North-South would even be mentioned in their communique.

Some discussion of East-West issues is expected, which may give Trudeau a chance to raise the question of crisis management, as he did at the 1980 talks in Venice. He has said that Western nations were caught completely off guard by the Soviet invasion of Afghanistan and the hostage events in Tehran and that mechanisms should be developed to provide a more concerted Western approach to crises.

The draft communique prepared in advance for the summit, according to officials, includes a statement of concern about nuclear proliferation coupled with an acknowledgment of the role of nuclear power and the need to speed up licensing of nuclear plants. Les Whittington Britain

LONDON -- Thatcher will be seeking support or at least the appearance of it for her economic course, particularly since Mitterand attacked it at the recent Common Market summit, stressing the primary importance of doing something about growing unemployment in the West.Britain will try hard to keep Mitterand from having the same impact with this argument in Ottawa, where they see Reagan as a key economic policy ally.

British diplomats say Thatcher in turn will try, in the words of one, "not to let the U.S. be put in the dock" for its high interest rates. This has been an integral part of Thatcher's early strategy, although Britain now would like the U.S. rates to fall and become more predictable.

On energy, Britain intends to help West Germany defend its natural gas deal with the Soviet Union -- critized by Washington last week -- as a good example of diversification away from Middle East oil and one that does not pose as much of a threat of dependence on the Soviets as the Reagan administration charged.

Britain expects much feeling-out on East-West issues -- including an apparently doomed initiative to persuade the Soviets to withdraw from Afghanistan by the foreign secretary, Lord Carrington -- in the many informal chats that Trudeau has arranged. Leonard Downie Jr. Japan

TOKYO -- japan's biggest worry is that it will be singled out for criticism from European countries for its export flood. Japan hopes not to be named as an offender in the final communique and expects that the document may vaguely warn against countries that concentrate exports in a few sectors, as Japan does, causing ruin to those domestic industries in other countries.

Japan's defense on this issue will be to warn again about the dangers of protectionism and plead for support for a free trade system. It will urge the industrial countries to prepare for "industrial restructuring" -- to abandon enterprises that cannot defend themselves against foreign imports or reorganize them so they can.

There may be trouble if Reagan pushes for a more restrictive trade policy against the Soviet Union. West Germany and France are likely to balk if he does, and Japan probably would support them, contending that all countries should be dealt with equally. William Chapman France

PARIS -- Reagan's reliance -- seen here as overreliance -- on high interest rates to stem inflation is hurting Mitterand's plans to pump-prime his way back from unemployment using cheap money. A corollary to this is France's complaint that the dollar is overvalued.

The oil producers sell petroleum in dollars so the French are paying a third more since the franc has taken a dive and many other raw materials are also dollar-priced, but Mitterand is given little chance of changing Reagan's tight money policy.

While France's interest in North-South issues contrasts with Reagan's apparent reluctance to get involved in multinational undertakings, observers think Mitterrand is going to have so much trouble on his plate so soon at Ottawa that he will have to forget about raising the issue of the Third World.

Mitterand and West Germany are in virtual agreement in opposition to Reagan administration policies in Central America, and this could be a topic in the political talks tonight. Jonathan C. Randal West Germany

BONN -- Despite all the noise Schmidt has made about high U.S. interest rates, his aides say he has decided not to seek a confrontation on the matter in Ottawa. He apparently was convinced during his Washington visit in May that Reagan has no intention of relaxing monetary policy for now.

According to a Schmidt economic adviser, the chancellor will be promoting the theme of free trade as his top priority. Bonn is concerned about protectionist pressures building in recession-hit countries.

With Bonn feeling sandwiched between America's tight monetary policies and the new French government's potentially inflationary expansive spending plans, free trade seems the safest theme to rally around.

"We need a positive message from the summit, not a negative one," said the adviser.

Schmidt is expected to underline European concerns that Western efforts toward the Third World countries not always take on an East-West framework. Schmidt will stress a policy of encouraging the nonalignment of Third World nations rather than using approaches that risk chasing them into the Soviet camp. Bradley Graham Italy

ROME -- Italians officials believe strongly that the summit talks should deal with both economic and political topics, which, Italian officials insist, cannot be separated. At Ottawa, they see international trade, the dollar and interest rates as the most timely and important themes.

"We do not expect a summit to operate as a magic wand that will miraculously solve complex problems," one Italian diplomat said. "Among other things they are far too short." He added, however, that the summits made a confrontation of ideas possible and even more importantly "serve to sensitize the Americans to the concerns of their free world allies."

Italian Foreign Minister Emilio Colombo said recently that the monetary issue is a major topic and that the Europeans will make a real effort to convince the Americans that they should not use monetary measures alone to fight inflation.

The other key theme, he said, would be international trade policy and the need to deal with growing protectionist implulses.

"The european economies are faced with the invasion, or, better put, the competition of the Japanese," he said, and added that it was not in Japan's interest "that Europe's industrial societies might risk crises in certain important sectors." Sari Gilbert