President Reagan and Canadian Prime Minister Brian Mulroney, opening two days of talks here today, attempted to smooth over their differences on acid-rain pollution by naming special envoys from each nation to examine the issue and report back next year.

Mulroney, who has been under political pressure to make progress on acid rain and end a long stalemate with the United States, said the agreement would "break a deadlock which has prevented some action on this."

Reagan, who has resisted any costly U.S. cleanup program for acid rain, said, "Together, we will find an answer to this problem."

As they arrived at the historic Chateau Frontenac hotel here for their first meeting, Reagan and Mulroney were met by several hundred protesters. Some carried umbrellas to protest U.S. inaction on acid rain. Others carried placards criticizing Reagan's foreign policy, including Central America and the nuclear arms buildup.

"Go home Yankee, go home!" some of the demonstrators chanted in French.

In a joint appearance before reporters, Reagan said former transportation secretary Drew Lewis, currently the chief executive of Warner-Amex, would be the U.S. special envoy. Mulroney named the former premier of Ontario, William G. Davis, as Canada's representative.

The duties of the new special envoys were left vague in a joint statement issued after a half-hour meeting between the two leaders. The statement, the result of an agreement hammered out in recent weeks by Ottawa and Washington, said the envoys will "pursue consultations on laws and regulations that bear on pollutants thought to be linked to acid rain."

The envoys are also to "enhance cooperation" in research on acid rain, seek improved exchange of scientific information and "identify efforts to improve the U.S. and Canadian environment."

When a reporter asked Reagan, "What are they supposed to do?" he said he could not answer questions but added, "We shall go forward with finding an answer to what is a problem that belongs to both of us."

Shortly after the announcement, however, White House spokesman Larry Speakes said Reagan "has not changed his basic view" that more research is necessary into acid rain before money is spent to clean it up.

Speakes said Reagan had an "open mind," but today's announcement would not require added spending for acid rain this year. He said the agreement places the issue "on a higher plane than before."

Mulroney recently announced a plan to cut sulfur dioxide emissions by half in eastern Canada over nine years, and he has said that more action is necessary than just research or study.

The announcement today seemed likely to provoke criticism from people in both nations that it did not go far enough.

Mulroney said the appointments of special envoys would "ensure this never finds it way again onto the back burner." He said the envoys have "uncommon access to us as leaders" and "they will carry the matters forward and I think help us achieve real results."

Acid rain is caused by emissions of sulfur dioxide and other chemicals from factories, coal-burning power plants, autos and natural sources on both sides of the border. The emissions mix with water vapor and are carried by winds before falling to the ground as a weak solution of sulfuric acid that is blamed for damage to lakes and forests in the northeastern United States and Canada.

By making the announcement quickly today, the two leaders appeared to be trying to put behind them the one issue that threatened to distract from their otherwise carefully planned celebration of U.S.-Canadian relations.

Reagan and Mulroney took time out to celebrate their common Irish heritage, swapping jokes as, on St. Patrick's Day, they opened the first meeting of what has been referred to as the "Shamrock Summit."

Wearing a bright green tie, Reagan noted in his remarks on arrival here that others were wearing green as well. "I will make my contribution tonight at dinner," he added. "I'm going to think of the prime minister's majority in Parliament and turn green with envy."

Mulroney invoked an Irish blessing "expressing the hope that the Lord always hold you and your people in 'the palm of his hand.' "

As they were driven across the snow-covered landscape from L'Ancienne Lorette Airport, Mulroney talked to Reagan about his meeting last week with the new Soviet leader, Mikhail Gorbachev, a senior Canadian official said. Gorbachev and the arms talks in Geneva are to be the prime topics in Monday's discussions.

In his arrival remarks, Reagan hailed the U.S.-Canadian relationship as "more than friends, and neighbors, and allies. We are kin."

Both he and Mulroney also acknowledged their differences. Reagan recalled that Franklin D. Roosevelt was the last American president to visit Quebec while in the White House and said he would follow Roosevelt's call for "frank dealing, cooperation and a spirit of give and take."

Due to erroneous information provided by Agence France-Presse, an officer of the Royal 22nd Infantry of the Canadian Army was incorrectly identified as a Royal Canadian Mounted Police officer in a photograph caption yesterday.