Secretary of State Cyrus Vance arrives in Peking Monday, restrained by President Carter's decision to postpone - though definitely not to reject - the aggressive new China policy urged on him by Peking-watchers in his administration.

That decision was made at a Washington meeting July 30 presided over by the President himself. In China Vance has authority to talk and listen - but not to grant the condition demanded by the Communist regime as the price for full diplomatic relations with Washington: abandonment of Taiwan.

Abandonment was unmistakably pointed to by a top-secret policy paper prepared by the administration's resident China experts, and that paper by no means has been repudiated. Rather, the July 30 meeting determined the time was not propitious for so dramatic a shift. "The thinking was," one official told us, "that an awful lot had been attempted in foreign policy, with not that many good results."

This suggests the President has not yet decided the China question, a difficult foreign-policy area where he has been tugged and pulled at by advisers. After the first hinting at the abandonment of Taiwan, candidate Carter shifted ground in the second presidential debate by pledging "the preservation of the independence and freedom of the people of Taiwan."

Sinologists brought into the Carter administration regarded this as a campaign "retreat" from the ambiguous Shanghai communique of February 1972, in which President Nixon moved toward eventual recognition of Peking to the exclusion of Taiwan. So a speech by Vance on June 29 went beyond the Shanghai communique by aknowledging the existence of only "one China," and one day later the President chimed in by promising only to "make sure that the peaceful lives of the Taiwanese [in] the Republic of China [are] maintained" - moving away from his campaign support of Taiwan.

Behind this rhetoric is one of Washington's most closely held and widely criticized documents: PRM-24, an interagency report on China policy. Although the style of listing competing options results in no formal recommendation, there is little disagreement that PRM-24 leads remorselessly to this policy:

A rapid rupture of diplomatic relations with Taiwan and abrogation of the U.S.-Taiwanese defense treaty, permitting full diplomatic relations with mainland China - this perhaps to be set up during Vance's trip to Peking. All U.S. governmental facilities would be pulled off Taiwan. However, military aid to Peking would be inadvisable for now.

Behind the smokescreen of competing options, PRM-24 is wrestling with these puzzlers: If diplomatic and military ties were broken with Taiwan, how could the island be protected? By military aid without a defense treaty? By coaxing Peking into some guarantee?

Whether or not the President's advisers finally realized they were facing an inherent contradiction, the consensus gradually grew in the administration's upper reaches that PRM-24 could not now be followed to its conclusion. The fact that Carter had his hands full - Israel, Panama, Korea, Cuba - was the reason for the July 30 decision to make Vance's journey a goodwill, explortory visit.

Even so, China policy remains in the hands of the three principal authors of PRM-24. Sinologists Michel Oksenberg of the National Security Council and William Gleysteen of the State Department want existing ties with Taiwan broken. The third collaborator, NSC Director Zbigniew Brzezinski, is far less interested in deserting Taiwan than in strengthening the U.S.-Peking link at the expense of Moscow.

The grey eminence guiding this policy is Sinologist Doak Barnett at the Brookings Institution, who warns that failure to formalize relations with Peking could provoke Sino-Soviet rapprochement. Harvard Professor Emeritus John K. Fairbank is the policy's father figure; his New York Times article urging the United States to meet Peking's demands for cutting ties with Taiwan is cited favorably by high-ranking U.S. officials.

PRM-24, the secret interagency document on worldwide U.S. military force structures, reflects the hold of the Barnett-Fairbanks thesis. It compares a "current presence baseline" (Alaska-Japan-Korea-Okinawa-Philippines) in the Pacific with a "reduced presence baseline" (Alaska-Japan-Okinawa-Guam); nowhere in the massive document is the military significance of Taiwan even mentioned. What reappears intermittently is fear of Sino-Soviet rapprochement.

Despite the administration's human-rights campaign, the moral argument against abandoning 17 million citizens of Taiwan who live in incomparably greater freedom than 800 million mainland Chinese does not interest the President's Sinologists. Less idealistically, the President might want to consider what the hard-headed gentlemen in Peking think of a superpower with so little faithfulness toward small allies. By giving Vance a limited mission, the President gives himself more time to compare the advice of his Sinologists with competing advice from others.