BEIJING -- Soviet President Mikhail S. Gorbachev arrived in Beijing today for the first Sino-Soviet summit in 30 years, ending the long and bitter conflict between the two great Communist powers.

Gorbachev's four days of talks with Chinese leaders, including Deng Xiaoping, the country's senior leader, are expected to complete the normalization of Sino-Soviet relations, which once were so tense that they brought the two nations to the brink of war, and to lay the basis for increased political and economic cooperation.

A pro-democracy protest by thousands of university students in Beijing's Tian An Men Square forced the Chinese leadership to hold the formal welcoming ceremony for Gorbachev at the airport, instead of the occupied square outside the Great Hall of the People, where it had been planned.

Gorbachev, with his wife, Raisa, in a white dress by his side, emerged at the door of the Ilyushin 62 aircraft exactly as scheduled at noon and descended the stairs to be greeted by Chinese President Yang Shangkun. As cannons fired a 21-gun salute, a People's Liberation Army band played the Soviet and Chinese national anthems, after which a single soldier marched in front of the Soviet leader, saluted and said, "Welcome comrade president."

Gorbachev and Yang reviewed an honor guard of about 150 army, navy and air force personnel and greeted officials from the Soviet Embassy. They laughed and smiled as they chatted with each other before Gorbachev got into a black limousine and sped away for downtown Beijing, where he was greeted by tens of thousands of spectators who lined the route.

In an arrival statement, which was issued at the airport ceremony, Gorbachev said he was visiting in the springtime, a season of "renewal and hope." He said Soviet Union believes the summit will "mark a watershed in relations" between the two countries.

"We in the Soviet Union follow with keen interest the transformations that are unfolding in China," the Soviet president said.

At mid-morning today, about 30,000 student protesters, supporters and onlookers were still gathered in Tian An Men Square, where the late afternoon welcoming ceremony had been scheduled.

The decision to move the welcoming ceremony to Beijing's old airport terminal marked a return to the old protocol in which visiting dignitaries were greeted immediately on their arrival, rather than later at Tian An Men Square.

Demanding a Dialogue

The demonstrators, including about 1,500 who began a sit-in and hunger strike Saturday, are demanding a dialogue with Communist Party and government leaders on ways to broaden democracy in China.

Zhao Ziyang, the Chinese Communist Party's general secretary, had urged the students not to disrupt the summit, the first between Chinese and Soviet leaders since 1959, and the party newspaper People's Daily called upon the students in a front-page editorial Sunday to "cherish the country's reputation."

Chinese authorities had issued orders that the square was to be closed to all pedestrians and traffic this morning, but the firm student protest upset this plan. Authorities have also announced that they plan to block off the square Tuesday morning, when Gorbachev is scheduled to lay a wreath at the Monument to the People's Heroes in the middle of the square, where the demonstrators are gathered.

Soviet officials, clearly uneasy with the Chinese protesters' demands for glasnost , the policy of political openness instituted by Gorbachev as part of increased democracy in the Soviet Union, refused to make any comment on the demonstrations except to say that Gorbachev's schedule had already been "finalized" when students pressed for a meeting with him.

Visit to Shanghai

On Tuesday, the Soviet leader will meet with Deng, Zhao and Premier Li Peng. Further talks follow Wednesday, and Gorbachev will visit Shanghai before leaving for Moscow on Thursday.

Gorbachev left Moscow on Sunday morning and spent the night in the Siberian city of Irkutsk.

In addition to his wife, Gorbachev was accompanied to Beijing by Eduard A. Shevardnadze, the Soviet foreign minister; Alexander N. Yakovlev, another member of the party's ruling Politburo who heads its Foreign Policy Commission, and Yuri Maslyukov, a Politburo alternate member, first deputy premier and the chairman of the Soviet State Economic Planning Commission.

China's top leader, Deng, speaking last week with visiting Iranian President Ali Khamenei, said that he and Gorbachev would "try to settle the disputes that have arisen between us over the past 30 years so as to normalize Sino-Soviet relations," the official New China News Agency reported.