Top Reagan administration officials are in the middle of a major reassessment of China policy before Secretary of State George P. Shultz's February trip to Peking, and are discussing U.S. unease at possible Chinese wavering on commitments to long-standing strategic interests in response to tempting appeals from Moscow.

Implicit in the administration's concern is the suggestion that Peking could complicate relations with Washington at a time when both countries instead might advance them, particularly in the area of energy development and possibly also military sales.

Underscoring the degree of interest in the U.S.-China-Soviet policy mix was a high-level seminar organized for Shultz and other top officials yesterday at the State Department. Many of the participants have been identified with former secretary of state Henry Kissinger, who was present, and almost all are known to have pressed in the past for closer ties with China while preserving an element of caution.

U.S. experts who have visited Peking recently say the Chinese are placing enormous importance on the Shultz visit, which begins Feb. 2, and note that his trip could be the first of several this year in a relationship that for the past decade has been oriented by top-level contacts.

"U.S.-China relations have never become institutionalized. It is a relationship that has been trip-driven, and this year there likely will be two or three major top-level trips," said one expert with long experience dealing with the Chinese.

The Pentagon is said to be laying the groundwork for a possible high-level visit to China in the spring, and Secretary of Defense Caspar W. Weinberger is believed to have expressed a desire to make the trip himself.

Administration officials also acknowledge that China's new premier, Zhao Ziyang, is a likely summer visitor to Washington, although a final decision is one of the signals that U.S. officials will be looking for during the Shultz visit. A visit by Zhao to the United States would set the stage for a trip to China by President Reagan, although such a visit has not yet been decided.

The spate of possible high-level U.S.-Chinese contacts follows several months during which there have been no such meetings. Even those of the first year and a half of the Reagan administration concentrated for the most part on binding the wounds inflicted by Reagan's pro-Taiwan campaign rhetoric, culminating in the communique of last August on the Taiwan issue.

During those months, big-power relationships have come unhinged, with leadership changes in the Soviet Union and China and Shultz's emergence in place of Alexander M. Haig Jr. as secretary of state.

At the same time, relations among the three big powers have become unusually fluid. U.S.-Soviet ties have become more contentious while Moscow and Peking suddenly are talking about breathing new life into their relations. Concurrently, the Chinese have moved to put distance between themselves and Washington.

Shultz heard the views yesterday of a star-studded cast of China experts, pulled together by Winston Lord of the Council on Foreign Relations and a former policy maker himself. The group included former defense secretary Harold Brown and former National Security Council experts William Hyland, Richard Solomon and Michael Ocksenberg.

Listening to their views, in addition to Shultz and the top echelon of the State Department, were Weinberger and National Security Adviser William P. Clark.

Observers of the U.S. policy process noted that there were no ardent pro-Taiwan advocates in the group nor were there many voices who would have spoken as forcefully as Haig or former national security adviser Zbigniew Brzezinski of using China as a counterweight to the Soviet Union.

Based on interviews with experts in and out of government, Shultz and the other policy makers most likely heard arguments in favor of meeting the Chinese on their own terms but making clear that their evolving relationship with Moscow affects U.S. interests not only in Asia but also in Europe.

Shultz, if past practice is followed, will take these views into counsel along with others from within the policy apparatus before formulating his own views to take to the president. Some intra-government discussions are believed to have taken place already.

The Chinese, who begin the next round of talks with Moscow just after the Shultz visit, have outlined three areas where they expect improvement from the Soviets if relations are to improve markedly: relaxation of tension along the Sino-Soviet border, withdrawal of Soviet troops from Afghanistan, and a shift in Soviet support for Vietnam and particularly for Hanoi's control over Cambodia.

At the same time, they also have outlined a policy of distancing themselves from Washington and equating the United States with the Soviet Union as a danger, albeit perhaps not as big a threat as Moscow.

"We have tried to treat them as a friendly, non-allied country. When they lump us with the Soviets as hegemonists China's term for a nation with imperialistic aims , that's not helpful," said one U.S. expert as the policy review got under way.

"If they make major shifts on the border question alone, that would be just a bilateral issue. The Chinese are making real efforts to win friends in Southeast Asia, and to make a change just in that area would be a charade. It would be destructive of their aims in the region and enhance suspicions of the Chinese."

Left unsaid was the fact that Chinese opposition to Vietnamese domination of all of Indochina, coupled with a lessening of active Chinese support for Communist parties elsewhere in Southeast Asia, dovetails with U.S. interests, as does opposition to an increased Soviet military presence in the area.

"Cambodia is the heart of the matter for the Chinese," said one administration official, a perspective reinforced by recent Chinese visitors to Washington.

The official indicated, however, that there were signs that China might consider a relatively modest troop drawdown by the Vietnamese in Cambodia as sufficient for movement on the Sino-Soviet front, a step that would leave untouched, for the short run at least, the Soviet air and naval presence at former U.S. facilities in southern Vietnam that have proven so worrisome to U.S. and Chinese strategic planners.

The Afghan issue remains in abeyance after signs of some movement by Moscow in mid- and late 1982. Recent Pravda editorials have taken a hard line on the issue, and the next likely signals would come during U.N. special negotiator Diego Cordovez's trip to Pakistan, Afghanistan and Iran later this month.

The Chinese, meanwhile, have been preparing for possible moves on the issue of the Sino-Soviet border, where both sides maintain hundreds of thousands of troops.

Unusual recent Chinese press accounts of conditions along the border noted that Soviet military exercises have been held much less frequently and that day-to-day problems have been more easily resolved.

The article noted that Soviet border forces are "no guard of honor" and added, "Superficially it would seem that there are traces of relaxation, but we will have to let further facts and actions judge whether or not it is a substantial one."

U.S. officials more concerned with Soviet affairs indicate that they believe that new Soviet leader Yuri Andropov is serious in pushing ahead with Brezhnev's moves toward China and believe the United States should take counter steps, particularly in the trade area.

"Andropov has a more Western European orientation. He may believe the previous leadership was a little hysterical about the Chinese threat. Soviet policy is increasingly Eurocentric," one high-ranking official argued.

"Andropov may be able to convince others that they can shift some resources over to Europe, in the sense of economic and propaganda resources, not just military. That is very important," the official said, referring to increasing Soviet efforts to wean the Europeans from U.S. leadership.

The official argued for "sending some signals" to the Chinese that the United States intends to solidify the relationship launched by former president Nixon and Kissinger a decade ago.

The "signals" would be in terms of increased access to U.S. technology, but the official acknowledged that the Pentagon and particularly the White House still were reluctant to move as rapidly as the Chinese might like.

There does appear to be room for movement, however.

Assuming the current talks in Peking on textile imports end on a moderately successful note, administration officials expect the Shultz visit, or subsequent trips, to result in U.S.-Chinese cooperation on developing China's vast energy resources.

In addition to further possible oil technology sales, officials in and out of government point to projects that are expected to reach billions of dollars in value in tertiary onshore recovery of oil, open-pit coal mining, port development and possible hydroelectric power development.

U.S. officials are keeping the closest watch on possible military sales, however, for hints of Chinese intentions.

The United States began to offer so-called "nonlethal" military equipment to the Chinese during the Carter administration. Haig, in his enthusiasm to develop a strategic relationship with China, upped the ante last year by winning Reagan's approval for direct military sales. The Chinese so far have not taken up the offer, apparently because of suspicions about U.S. arms policy toward Taiwan and suspected continuing antagonism within the Chinese Army leadership toward the United States.

Now, however, officials indicate that there is discussion under way for possible sale of "defensive" weaponry to Peking. An early test case is believed to be Chinese interest in antitank weaponry. Administration officials say such sales, designed to boost China's defensive capabilities against the Soviets, would not have to be balanced by arms for Taiwan, although they anticipate some congressional opposition.

This arms-sale approach nevertheless would be far less ambitious than some of the ideas floated when Haig first made the arms offer, perhaps reflecting a more cautious approach by Shultz. Waiting in the wings are other possible deals, according to U.S. experts, who note a Chinese need for updating their own tanks with advanced armor plate.