"We're not going to turn our backs" on the people of Taiwan, Secretary of State George P. Shultz said yesterday, claiming that "they fought on our side" in the Korean and Vietnam wars.

Shultz's comments to the Conservative Political Action Conference, together with new statements on the subject by President Reagan, are likely to stir controversy in the People's Republic of China. During a trip to Peking two weeks ago, Shultz was repeatedly confronted with Chinese objections to U.S. ties with Taiwan.

The statements of Shultz and Reagan tended to minimize the U.S. commitment last Aug. 17 "to reduce gradually" the sale of arms to Taiwan, "leading over a period of time to a final resolution." This was the central U.S. undertaking in a Sino-American communique intended to surmount a deadlock on the Taiwan issue.

In response to a critical question at the conservatives' meeting, Shultz described the Aug. 17 communique as saying that "the level of arms needed by Taiwan basically is a reflection of the conditions that exist."

He added, "If there is a peaceful situation, one would expect the level of armaments to decline." Shultz laid great stress on Peking commitments to seek a peaceful resolution of China's problems with Taiwan, which it considers a wayward Chinese province.

There was no clear explanation for Shultz's statements that Taiwan "fought on our side" in the two wars. A State Department spokesman said that in the Vietnam war "we used air bases in Taiwan for logistical staging areas and repair facilities." About the Korean war, the spokesman could say only that Shultz had been "speaking in a broad sense." As far as is known, Taiwanese troops were not involved.

Reagan's latest comments, in an interview with the conservative publication Human Events, were that "we did not give an inch" in last August's Sino-American communique about Taiwan.

"If the day ever comes that those two China and Taiwan find that they can get together and become one China in a peaceful manner, then there wouldn't be any need for arms sales to Taiwan," said Reagan.

"And that's all that was meant in the communique. Nothing was meant beyond that. We're not going to say, 'Well, just as time goes by, we're going to reduce arms to them.' "

Reagan also said, in a comment which was unexplained, that "we are making progress in other areas that ensure that the representatives and people of Taiwan are treated with the respect which the American people demand."

He went on to say that, at the same time, it would be foolish not to pursue good relations with the People's Republic of China. "Three previous presidents felt it was important, and there remain solid reasons for doing so. But not at the expense of Taiwan."