Republican presidential nominee Ronald Reagan flew to this hot Texas city today to talk religion and morals to a gathering of Christians, but immediately found himself skewered again over his recent statements calling for an official relationship with Taiwan.

Reagan tried to dodge questions on the subject at a news conference here, but when pressed by reporters, he stood by his controversial call for an upgrading in U.S. ties with Taiwan.

Reagan has made it clear that he wants to keep the same relations the United States now has with Peking, while renewing an official relationship with Taiwan. He has refused to acknowledge that the People's Republic of China would consider such an upgrading in Taiwan ties to be, in effect, a "two-China" policy and a violation of the agreement the Carter administration made with Peking in 1978.

Pressed today on whether he stood by his controversial statement of last week, which was sharply criticized by Peking, he said, "I guess . . . yes."

Reagan's vice presidential running mate, George Bush, left last week on a trip to China. At an airport sendoff, Reagan said that under the terms of recent legislation on Taiwan, he proposed to establish government-to-government relations with that country. The Taiwan Relations Act does not provide for such government-to-government relations.

Peking adamantly opposes official U.S.-Taiwan ties.

Advisers to the former California governor had sought to soften his stand on the potentially explosive issue. In Peking, Bush has tried to reassure the Chinese on Reagan's position, saying that a Republican administration could not legally establish an official government liaison office on Taiwan. Bush added that he had no knowledge that Reagan intended to do so should he be elected.

Since 1971, when he visited Taiwan as an emissary for President Nixon, Reagan has ardently supported U.S. relations with Taiwan. The public relations firm of two of his closest advisers has been on the Taiwan government's payroll since 1971.

Pressed by reporters here today on the apparent conflicts in his position, Reagan denied that he favors a "two-China" policy, and said that he would be more specific "when George gets back"from China.

Reagan added at one point that his concept of some kind of improved relationship with Taiwan might "make a little more open and less hypocritical the situation that exists today."

He said that though the United States does $10 billion worth of business annually with Taiwan, the U.S. representatives there cannot talk to their Taiwanese counterparts in government offices, but must meet elsewhere. (The U.S. liaison office in Taiwan operates as an unofficial, nongovernmental "institution.")

Reagan came here to address a rally of fundamentalist Christians.

Greeted with a thunderous standing ovation, he preached a Republican gospel, saying that if he is elected, he will put religious morality back into government, with a special emphasis on the "primacy of parental rights and responsibility."

His appearance here was part of a Republican bid for the votes of millions of born-again Christians who have traditionally refrained from political involvement. The two-day rally in Reunion Arena grew out of a fledgling movement to get out the fundamentalist Christian vote.

The Republican nominee put to a test his sought-for image as a moderate by venturing into this ultra-conservative throng, where his two presidential opponents, President Carter and John B. Anderson, both reportedly had declined invitations to tread.

In his prepared statement, Reagan skillfully skirted any mention of such topics as homosexual rights, abortion and the Equal Rights Amendment -- all flash-point issues on which the evangelical Christians have stood in uncompromising opposition. One of the rally's organizers, for example, refers to the movement to pass ERA as an "immoral, perverted cause."

Reagan, on the other hand, went out of his way in his acceptance speech at the Republican National convention in Detroit to be conciliatory on that subject even though the Republican platform does not endorse the ERA.

In his address prepared for tonight he denounced critics who he said seek to exclude religious groups from participating in the political process. Their tactic is a cynical attempt "not only to discredit traditional moral teachings, but also to exclude them from public debate by intimidation and name-calling," he said.

Referring to a charge by some religious leaders that the fundamentalist organizers are violating the doctrine of separation of church and state, Reagan said, "The First Amendment was written not to protect the people and their laws from religious values but to protect those values from government tyranny."