In his first substantive accomplishment as the new chairman of the Senate Foreign Relations Committee, Sen. Frank Church (D-Idaho) has devised compromise legislation expressing a strong but imprecise U.S. interest in the future well-being of Taiwan.

Key Senate Republicans have accepted the Church compromise, and the Carter administration has given its grudging approval. Church and his associates predicted yesterday that the full Senate will also go along.

The Church compromise says "it is the policy of the United States... to consider any effort to resolve the Taiwan issue (i.e., reunification of Taiwan with the mainland) by other than peaceful means a threat to the peace and security of the Western Pacific area and of grave concern to the United States."

The compromise language also states that "the United States will maintain its capacity to resist any resort to force or other forms of coercion that would jeopardize the security or social or economic system of the people on Taiwan."

The administration can live with this language because it does not state that any use of force against Taiwan would be considered a threat to the United States, and because it contains no reference to the "integrity of Taiwan," a phrase that suggests Taiwan is separate from China. (Both the Taiwanese and the Peking governments take the position that Taiwan is part of China.)

Both those points were included in a draft proposed two weeks ago by Sen. Jacob K. Javits (N.Y.), the ranking Republican on the Foreign Relations Committee. Church was anxious to win bipartisan support for whatever measure came out of the committee, and he ardently courted Javits' acceptance of the compromise. The New York Republican gave in on Tuesday in a drafting session with Church.

The new legislation is expected to be adopted today by the Foreign Relations Committee. It will be a section of the administration's bill establishing a new legal basis for U.S. relations with Taiwan in light of the normalization of relations with the People's Republic of China.

President Carter has threatened to veto the legislation if it includes any declaration of support for Taiwan that would undermine the understandings reached with Peking that made normalization possible.

Yesterday Douglas J. Bennet, Jr., assistant secretary of state for congressional relations, said "we can live with" the new compromise. "But I'm not saying I'm happy with it," he added.

In effect, the Church-Javits compromise language will test China's willingness to accept in American law assertions that the Chinese Vice Premier Teng Hsiao-ping, has made in conversation with U.S. senators.

In early January, Teng told a group of senators that Taiwan could retain its own economic and social system and its armed forces, provided it accepted Chinese sovereignty in principle.

Achieving an acceptable compromise draft has not been easy for Church and his associates. They got off to a bad start two weeks ago when Javits' original draft was circulated to committee members as a "Javits-Church" document. This angered the administration and upset senators who opposed Javits' hardline approach, which included borrowing language directly from the Taiwanese-American mutual defense treaty that will expire at the end of this year.

Church retreated from that draft and began working on a new one. His efforts, which continued during the 12-day congressional recess, ended successfully Tuesday morning.

Several committee members said Javits had made key concessions, but an aide to the senator said he had only compromised "on phraseology, not on principles."

Javits told reporters yesterday he considered the new version as good as a treaty with Taiwan. Church disagreed, noting that this was a unilateral U.S. statement and had none of the "mutuality" of the old defense treaty with Taiwan.

Knowledgeable participants in the process speculated last night that Javits accepted the Church version because he decided it was the best he could get through the Foreign Relations Committee. Javits worked closely through this episode with Senate Minority Leader Howard H. Baker Jr. (R-Tenn.), who also endorsed the compromise yesterday.

So did senators who had favored a milder statement of U.S. support for Taiwan, including John Glenn (D-Ohio) and backers of a softer version proposed by Sens. Alan Cranston (D-Calif.) and Edward M. Kennedy (D-Mass.). Conservative Republicans are expected to oppose the Church version.

The House Foreign Affairs Committee is also considering this legislation, and is expected to approve language similar to Church's.