Peking and Moscow talk up trade. But the socialist powers skirt contentious political and military issues

As Chinese Vice-Premier Yao Yilin leaves for Moscow today, he carries with him some of the same questions about the Kremlin leadership that diplomats in the West are asking. Does the livelier face of Soviet foreign policy under Mikhail S. Gor-bachev offer prospects for more flexibility and compromise? Will the new foreign minister, Eduard Shevardnadze, bring fresh thinking to the Soviet Union's relations with the world?

The Chinese leaders are watching and waiting for answers along with everyone else. They have been heartened by Mr. Gorbachev's statements affirming his interest in improving Soviet relations with China. Yet their expectations are low that the new style of Soviet foreign policy offers much that is new in the way of compromise on the major issues dividing the two socialist neighbors.

Vice-Premier Yao's visit to Moscow has been planned for more than six months, since the ground-breaking trip to China by Soviet Vice-Premier Ivan V. Arkhipov last December.

It will highlight the slow but steady improvements that have been taking place in Sino-Soviet relations since 1982.

Before leaving Moscow, Mr. Yao is expected to sign a five-year trade agreement which aims to increase the value of two-way trade about four times by the end of the decade, from an estimated level of $1.6 billion this year.

Yao is also expected to sign an economic assistance agreement for the modernization of up to two dozen Chinese factories and to agree to increase the number of educational and academic exchanges to as many as 400 students and teachers.

At present there are about 60 Chinese and Soviet students studying in each other's countries and there are no known Soviet advisers in residence in China.

The progress in trade, other economic relations, and educational exchanges skirts political and military issues.

The most pressing of these is the deployment of the Soviet Red Army along their mutual border.

Last week, veteran mililtary leader Yang Shangkun, vice-chairman of the Chinese Communist Party's Central Military Commission, made the bluntest protest in years about the Soviet military threat.

In describing China's plans to cut 1 million troops from the People's Liberation Army by the end of next year, he said the number of guards on China's northern frontier had been reduced, ``in sharp contrast to a superpower's deploying a million troops along the Chinese border,'' according to the New China News Agency.

He said that in China's determination to promote peace, ``We have put our views into practice.''

According to Western diplomats, the Soviets have but 500,000 troops in some 52 divisions along the border, facing 58 Chinese divisons. The Soviets have five times as many tanks and armored personnel carriers as the Chinese, the diplomats say.

The other obstacles to more normal relations with the Soviet Union, according to Chinese leaders, are the Soviet Red Army's occupation of Afghanistan, which touches China's western-most region of Xinjiang, and Soviet support for Vietnam's occupation of Kampuchea (Cam-bodia).

There are no signs that China has softened its concerns on these issues, though three months ago, on the eve of semian-nual political discussions, China's leaders tried to brighten the prospects for Soviet compromise by temporarily forgetting what the oft-repeated three obstacles were.

In a recent interview, one of China's best-known experts on international relations and a senior adviser to the state council said he expected China's relations with the Soviet Union to essentially stand still for the time being.

``I expect for the immediate and foreseeable future that Sino-Soviet relations will stagnate,'' said Huang Xiang, director of the Center of International Studies, a research and advisory group under the state council.

``I mean by that, not much improvement, and no retrogression either. . . . But I think relations between China and the Soviet Union eventually will have to improve. How can you expect the two countries to stand looking at each other with angry eyes and grinding their teeth?

``We are groping for ways to improve our relations, but it will take time to make progress,'' Mr. Huang told the foreign press two weeks ago.