The Quebec separatist government of Premier Rene Levesque suffered a crushing defeat today as voters decisively rejected its bid to lead the French-speaking province toward political independence from Canada.

The astounding victory for the supporters of Canadian unity in this predominantly French-speaking province appears to remove the threat of Quebec secession and opens the way for constitutional changes to meet Quebec's aspirations.

A dejected Levesque accepted the defeat before a tumultuous crowd of supporters, hundreds of them weeping openly. Levesque said the people of Quebec "have clearly given the federal Canadian government "one more opportunity" to make constitutional adjustments.

Apparently seeking to defuse tension and bitterness in the separatist camp, Levesque held out hope that at some time in the future there will be another attempt to seek independence.

"I have faith that some day we will have another meeting with history and that we will be there together. But I can't see when," Levesque said.

With 98 percent of the approximately 3.5 million ballots counted, the federalist forces of Liberal opposition leader Claude Ryan had 59.4 percent of the vote with Levesque's Parti Quebecois holding 40.6 percent. Most importantly, the federalists appeared to have won slightly more than half of the French-speaking votes. The French speakers account for 80 percent of Quebec's 6.3 million population.

Ryan hailed the outcome as demonstrating that Quebec residents want "to seek their future along the path of Canadian federalism." But he made it clear that he is deeply committed to radical constitutional changes.

Obviously addressing English-speaking Canada, Ryan said, "Our future will not be easy to build. But the action of today calls for changes, and these will have to be made in the federal system so that it becomes acceptable and more solidly rooted in the hearts and minds of Quebecers and all Canadians."

Prime Minister Pierre Trudeau, a native of Quebec whose career has been based on his struggle against separatism, called the outcome a "reaffirmation of our will to live together" and said it was one of the happiest days of his life.

He appealed to all Canadians to "strengthen and renew the Canadian federation."

Despite some fears that there would be violence among the deeply divided French-speaking population of this province, most of Quebec seemed to react calmly to the outcome of the referendum. Some scattered acts of violence were reported in the upper portions of Quebec City, however, and police patrols were heavier than normal.

Today's vote capped five weeks of campaigning that presented an agonizing choice for most Quebecers. It was perhaps best summed up by a close aide to Trudeau Monday night. "Regardless who wins, we'll all lose a little," the aide said.

The outcome represents a symbolic rather than final decision. Quebec's 4.3 million eligible voters were asked whether they would give Levesque the mandate to negotiate sovereignty within the framework of an economic association with the rest of Canada.Any actual changes would have had to be approved in another referendum.

But Trudeau, Ryan and other federalist supporters repeatedly warned that a Levesque victory would be an irrevocable step toward some form of political separation from Canada.

It is uncertain how the other nine Canadian provinces, each with its own personality and economic objectives, would react to today's outcome. Trudeau had pledged to initiate constitutional negotiations without giving any hints as to whether he is prepared to abandon his longstanding opposition to "special status" for Quebec.

Trudeau sent a letter to all provincial premiers calling for an immediate constitutional conference, Canadian television reported tonight.

The mainstream of Quebec opinion, which embraces both Levesque's and Ryan's forces, has been in favor of more power for the provincial government while keeping the federal government in Ottawa at arm's length.

Although the separatists want to achieve political sovereignty, they envision a high degree of economic, military, and diplomatic integration with the rest of Canada. This would include a monetary trade and customs union.

Ryan, who has assailed Levesque and his proposals, is an equally forceful Quebec nationalist with aims differing from those of the Parti Quebecois only in that Ryan believes they can be achieved without separation.

As a result, this is one of the most difficult moments in Canada's 113-year history. Quebec with its 595,000 square miles is the largest of the 10 provinces and second only to Ontario in population. Until recently, French-speaking Quebecers maintained a distinct cultural identity as an inward, rural people dominated by the Roman Catholic Church who had left commerce and industry to the English-speaking, Protestant minority. The minority assumed economic power that has persisted to this day.

But in the past two decades, the French speakers of Quebec have broken out of that mold and have moved swiftly to urbanize their culture and educate the younger generation in unprecedented numbers. A new French-speaking elite has not only challenged but also has sought to assert greater political authority and has pursued an international role for Quebec.

Levesque formed the Parti Quebecois in 1968 in response to a popular desire to protect Quebec's special ethnic character and safeguard its economic interests in the Canadian federation dominated by the English-speaking majority.

After sweeping to power in 1976, the Parti Quebecois has managed to retain its hard-core separatist supporters while it gained backing from many people who oppose independence but favor changes in the federal system.

At the beginning of the campaign, polls showed Levesque's forces in a clear lead. But two weeks ago, the opponents of separation began to gain ground.

In the final two weeks, a massive federalist publicity drive was aimed at undecided voters. Light planes droned over Quebec trailing banners reading, "We love you Quebec" that were signed by cities and provinces from across Canada.

Editorial writers throughout English-speaking Canada yesterday appealed to Quebec voters to reject independence and offered pledges for major constitutional revisions.

The tone was caught in the influential Toronto Globe and Mail, which said: "It should be recognized by Canadians outside Quebec that when we urge the people of Quebec to vote "no," we are committing ourselves to the negotiation of change, real and possibly wrenching change, in the structure of confederation as we know it."

For Quebec, this has been a wrenching experience. An illuminating story was told by a Canadian Broadcasting Corporation producer, who, before the outcome was known, wanted to have Monique Begin, a member of the federal Cabinet and Ryan supporter, debate the results with her sister, a Montreal schoolteacher and Levesque supporter, on a radio program Wednesday morning.

"Do you think i'd be able to even talk to my sister Wednesday morning?" Begin replied, rejecting the offer.