Peking — At a time of coolness in relations between Peking and Washington, relations between China and the Soviet Union are showing signs of a slight thaw - at least at the fringes.
The Chinese have said there will be no significant progress in restoring ties with Moscow until the Soviets match deeds with words. This was the response given by Peking in March to Soviet leader Leonid Brezhnev's statement that ''We are prepared to come to terms without any preliminary conditions on measures acceptable to both sides to improve Sino-Soviet relations.''
Nonetheless, a modest warming of relations between the two big communist powers has been symbolized recently by a growing catalog of low-level contacts. These range from semiofficial contacts in both Moscow and Peking to academic and sporting exchanges. Soviet athletes, for example, competed in Peking last month at the invitation of the Chinese government - the first such exchange in 16 years.
Chinese officials insist that any marginal improvement in China's relations with the Soviet Union has nothing to do with their exasperation with the United States over arms sales to Taiwan - although it does seem likely to have colored recent Chinese criticisms of the US.
The view among Western diplomats here is that China has decided to steer a middle course between the superpowers by emphasizing its traditional links with the third world. In fact, China has made a determined drive in recent months to improve its standing among third-world countries. This partly explains its recent sharp attacks on US policies in the Middle East and South Korea, and of Washington's unwillingness to sign the Law of the Sea Treaty.
Does all this add up to the beginnings of a real thaw in the more than 20 -year freeze in relations between Peking and Moscow?
The answer is not simple. According to an experienced Asian diplomat in Peking, whose country has a direct strategic interest in any movement in China-Soviet relations, the changes now taking place are of a ''functional'' rather than ''fundamental'' nature.
In other words, there is some movement on the fringes of the relationship, but basic differences remain that would make it difficult for the Chinese and Soviets to normalize relations. But it is interesting to note developments since the middle of last year.
* In October 1981, the Soviet Union proposed the resumption of stalled border negotiations, adjourned in 1978. China said it would study the proposal. It has not yet agreed to a resumption.
* In February this year, Soviet Prime Minister Nikolai Tikhonov told Japanese journalists in Moscow that the Soviet Union was ''not going to keep from concrete steps'' toward improved relations. But he added that the process must not be one-sided.
* In March, three Chinese economists visited Moscow to study Soviet planning procedures. They were reportedly received by Alexander Bachwrin, the deputy chief of the state planning commission.
* In May, the head of the Far Eastern department of the Soviet Foreign Ministry, Mikhail Kapitsa, visited Peking. He was received by Chinese officials. While Mr. Kapitsa was here, a signed article published in Pravda expressed the hope that Peking would ''find a way out of the blind alley'' in which Soviet-Chinese relations are at the moment.
* In late May, a delegation representing the China Council for the Promotion of International Trade visited Moscow to explore trade opportunities.
* Earlier this year Chinese authorities decided to give more weight to studies of the Soviet Union. This decision was taken at senior levels of the Chinese Communist Party and reflects recognition that in the years of extreme anti-Soviet feeling in China studies of the Soviet Union were let slide.
After years of almost complete estrangement (apart from border discussions which made no progress and annual trade negotiations), it appears the two countries are taking limited steps to place their relations on a more normal footing.
This does not mean, however, that China is dropping its basic objections to what it describes as Moscow's ''hegemonistic'' policies, as shown by the Soviet invasion of Afghanistan and its backing for Vietnam's occupation of Kampuchea (Cambodia).
The most recent authoritative Chinese view of the state of Sino-Soviet relations was given by Chinese Premier Zhao Ziyang on his visit to Tokyo last month. He told his Japanese counterpart, Zenko Suzuki, that there had been ''no changes'' in the relationship.
''We have noted that Soviet leaders said they wanted to improve Sino-Soviet relations, but they haven't taken any practical action,'' he said. ''We have always held that the question of Sino-Soviet relations should be settled through negotiations, but the Soviet Union shows no good faith.''
While, on the face of it, this expression of the Chinese position gives little encouragement to the view that a limited thaw is taking place, it does not foreclose the possibility of an improvement in relations through negotiations. If, say, the Soviet Union indicated it was prepared to withdraw some of its million-strong forces from China's border, this would almost certainly be considered a significant enough gesture of good faith for the Chinese to review their anti-Soviet position.
It is doubtful that the present Soviet leadership would consider such a gesture. Mr. Brezhnev's Chinese phobia would probably not allow it. But Peking is likely to be looking forward to the post-Brezhnev era and may have concluded the climate for negotiations will improve.
A Western diplomat here describes the situation as ''fluid,'' in the sense that there is some movement in the relationship whereas before there was virtually none. The diplomat said that ending of the Brezhnev era could well turn out to be a catalyst for significant progress toward a return to normal relations, though there is absolutely no chance of a restoration of the cozy relationship of the 1950s.
It is likely, observers say, that contacts will continue to grow on the fringes of the relationship - perhaps developing a momentum of their own which would have the effect of pushing the two sides closer to each other.
The consensus among Western diplomats in Peking is that there is little chance of a rapprochement as long as 45 Soviet divisions remain on China's borders, and as long as Soviet troops remain in Afghanistan. But these same diplomats say that the huge economic problems facing the Soviet Union, plus its having to contend with three ''power centers'' - Europe, China, and North America - may eventually force Moscow into making concessions.
For the time being, Chinese policy is likely to continue on two levels. While acceding a limited improvement in state-to-state relations, China will continue its criticism of and opposition to the Soviet Union in international forums. This may seem a contradictory position. But it is one the Chinese will have no trouble maintaining indefinitely, if necessary.
A further estrangement with the US over Taiwan, if it were to occur, is not likely to lead to a change in China's basic political strategy toward the Soviet Union.