The Rev. Billy Graham said today that he encountered no restrictions on what he said during a six-day visit to Moscow and that, while there were differences in how religion is practiced here and in the United States, "that does not mean there is no religious freedom" in the Soviet Union.

The 63-year-old American evangelist, once an outspoken critic of communism, startled a news conference by asserting that he found Moscow churches packed to capacity and adding, "You would never get that in Charlotte, North Carolina."

The churches in which Graham preached were filled with security agents. Only about one-third of the congregations were local believers, and most of them were women. Foreign visitors, including persons attending the same religious conference on disarmament Graham came for, also made up about a third of the congregations.

When U.S. reporters asked Graham whether he had attempted to learn the fate of a young Bapist woman who was taken into custody after she unfurled a banner from a balcony at the end of his sermon Sunday at Moscow's Baptist church, he replied:

"Some people can be detained for all kinds of reasons. We detain people in the United States if we catch them doing things wrong. I have had people coming to my services in the United States and causing disturbances and they have been taken out by the police."

The young woman quietly brought out the banner after Graham had finished his sermon and held it up for about two minutes before folding it again. The banner, in English, read, "We have more than 150 prisoners for the work of the Gospel."

Baptist sources said today that the woman was still in detention.

During the news conference, the evangelist said his visit here was "the most intensive period of time in my entire ministry" and that he was departing from here with his heart "strangely warmed." He said he was "going away with a great many positive viewpoints," convinced that both the United States and the Soviet Union were "searching for peace."

Commenting on the treatment he has received, Graham said, "The meals I had are among the best I have ever had," Graham said. "In the United States you have to be a millionaire to have caviar and I have had caviar with almost every meal I've had here."

A four-ounce jar of caviar, which is available only at Moscow's hard currency shops, sells for about $55, or roughly one-fourth of an average monthly wage in the Soviet Union

Graham was the most prominent figure at the disarmament conference, which was sponsored by the Russian Orthodox Church.

The American evangelist was also received today by Boris Ponomarev, an alternate member of the ruling Politburo. At a joint news conference later Graham was asked for his reaction to a statement by Metropolitan Paulos Mar Grigorios of the Orthodox Church of India who had praised the gathering as being "significant in dispelling the false notion that there is no religious freedom in this country."

Asked whether he agreed with that statement, Graham said: "That is a relative term, I think. Of the various countries I go to in the world, of which there are over 50, there are various kinds of restrictions, various kinds of laws and formulas.

"It would be impossible for me to come to Moscow and in six days make any kind of evaluation. There are many differences in religion here and in the way it is practiced in the United States. But that does not mean there is no religious freedom" in the Soviet Union. Graham added: "I have experienced total liberty in what I wanted to say."

His aides earlier said privately that Graham did not want to do anything that might embarrass his hosts and that he wanted "to develop this relationship." There has been speculation that he expected to be permitted to return here for a preaching tour.

However, religion has an ambiguous place in an atheist state that does not tolerate competition with its official Marxist-Leninst ideology. There are no official figures on church affiliation in the Soviet Union. Nevertheless, some analysts estimate that among this country's 265 million people there may be as many as 30 million Russian Orthodox Christians, 5 million Roman Catholics, about 3 million Jews, 2 million Evangelicals and 30 million Moslems.

Comparatively speaking, organized religion has had an easier time during the past 15 years after almost five decades of unrelenting antireligious struggle conducted by the state.

During the period since President Leonid Brezhnev came to power, the state and church seem to have established a tenuous compromise under which organized religion, and specifically the Russian Orthodox Church, have been allowed to function provided they do not engage in proselytizing or work against the state.

The church, in turn, has offered public support to Soviet foreign policy initiatives. The disarmament conference is one example of such activities.

The Soviet media has continued almost daily attacks on religion, and scientific atheism is promoted throughout society, ranging from schools to factories. Authorities also confiscate religious books and have established an elaborate system of regulations, checks, and informal discrimination against believers.

Religious groups seeking to operate outside the framework of the officially sanctioned religion have been harassed persistently and their leaders imprisoned.