Republican presidential nominee Ronald Reagan, seeking to end the controversy over his intentions toward China and Taiwan, said today he seeks to do no more than Congress authorized last year in the Taiwan Relations Act.

His previous calls for the establishment of "official" or "government-to-government" relations with Taiwan actually meant that he simply wanted to carry out that act of Congress, Reagan insisted at a press conference with his runing mate, George Bush, who had just returned from a trip to China.

The difference between him and President Carter, Reagan said, is that "I would not pretend, as Carter does, that the relationship we now have with Taiwan, enacted by our Congress, is not official."

However, Reagan today dropped the phrasing he used in a press conference on Aug. 16, when he said he wanted an "official governmental relationship" between the United States and Taiwan. That terminology would appear to contradict the Taiwan Relations Act, which calls explicitly for U.S. Taiwanese relations to be conducted by a "non-governmental" instrumentality.

In Washington, a source who had participated in communications between Taiwanese officials and aides to Gov. Reagan said today that the Taiwanese had urged the GOP candidate to "back off" his earlier statements. The source, a legal expert on the Taiwan Relations Act, said Reagan appeared to do just that.

Also in Washington, Assistant Secretary of State Richard Holbrooke said Reagan's latest statement suggests "that he is trying to have his cake and eat it, too. He wants to offend the Chinese less than he did, but still wants to say that if he were president he would improve relations with Taiwan."

Reagan acknowledged at today's news conference that he had "misstated" his position in the past, but insisted that a nine-page statement he issued here cleared up the question of his China policy once and for all. The main thrust of that statement was that Reagan plans to upgrade American-Taiwanese relations without violating the Taiwan Relations Act, which does stipulate a nongovernmental, quasi-official relationship.

The flap over Reagan's attitude toward China has simmered for much of the spring and summer, and escalated onto the front pages after that Aug. 16 press coference. Before the Republican National Convention in July, Reagan said repeatedly that as president he would upgrade relations with Taiwan making them "official" or "governmental."

This rhetoric alarmed the Chinese government in Peking, which insisted on the downgrading of American relations with Taiwan as a precondition for establishment of full diplomatic relations with the United States. Publicly and in diplomatic messages conveyed to Reagan, the Chinese protested against his stated intentions.

In July, Reagan's principal foreign policy aide, Richard V. Allen, made a formal statement to the Republican Platform Committee declaring that Reagan had no intention of "turning the clock back" in relations with China, and would not try to fundamentally alter the U.S. relationship with Peking or Taiwan. Allen's statement appeared to be a change in Reagan's position.

Then on Aug. 16, at a press conference called to send off Bush on a trip to Japan and China, Reagan reverted to his old position, calling for "government-to-government" relations with Taiwan. This infuriated the Chinese, who proceeded to give vice presidential candidate Bush a frosty reception and then to pronounce his visit to Peking a failure.

Reagan today blamed much of the flap on "a distortion of my position that has been picked up by the Chinese press." He pledged that a Reagan-Bush administration would improve U.S. relations with both Peking and Taiwan.

"The issue is not how I feel about Taiwan," Reagan said. "The issue today is the Carter foreign policy and what it is doing to our allies and to the United States' position in the world."

That indeed was what the Reagan camp hoped the foreign policy issue would be in this year's campaign. But the White House has watched the Republicans' confusion over Taiwan gleefully, and clearly thinks it has an issue for the fall.

Campaigning in New York state today, Vice President Mondale said Reagan's "confused and misinformed positions" could have "disastrous consequences to our national security," and would "give cheer to only one major nation on earth -- the Soviet Union."

The Carter administration advertises the establishment of full relations with Peking as one of its major accomplishments, and as a useful step to help contain the Soviet Union.

Reagan today argued that it is "a transparency and hypocritical to pretend that an act passed by the United States Congress resulting in an agency or a foundation created by a government agency, manned by government employes -- who even though they are on leave of absence have all the prerequisites that existed when they were on active duty with the government --and funded by our government, is not indeed an official relationship."

Reagan was referring to the American Institute in Taiwan, which now represents the U.S. government there.

But asked whether a Reagan administration would make the American office on Taiwan official, the former California governor said, "No, it would be what the Taiwan Relations Act says it is." And he also said, as he did on Aug. 16, that it is "demeaning and insulting" for Taiwanese and American officials to be unable to meet one another in government offices. "This is at the discretion of the president and this is his decision. That is an order I would rescind."

Asked if, as president, he would reestablish diplomatic relations with Taiwan, Reagan said, "No. This is the very thing where the misunderstanding lies, and I have to say that this came from a distortion of my position that has been picked up by the Chinese press."

Bush, who returned from China Sunday, said that although Reagan had not yet announced all the specifics of what a Reagan administration-Taiwan relationship would be, "there's no question that Peking will be unhappy. We're bound to disagree . . . I don't think you have to know anything about the China equation to suggest that some of these things would cause heartburn in Peking."

Bush contended, however, that his trip to China had not been the "failure" that it was labeled in the Chinese press. He said he had gone to the mainland for a "frank exchange of views," not to pound out an agreement."