Soviet authorities today suppressed eight books from among thousands displayed here at the opening of the first Moscow international book fair.

American publishers' representatives protested the censorship at an hour-long conference with fair organizers, but were told that the ban on the volumes - which included "1934" and "Animal Farm" by George Orwell, both classic fictional treatments of a police state; a study of the Soviet secret police and a history of modern American poster art - was a "customs matter."

It was unclear last night whether any of lthe banned books would be cleared for display in the two cavernous exhibition halls where some 1,300 publishers from around the world are showing their volumes.

The fair has received a substantial buildup by the Kremlin, with the official press calling it an example of the Soviet Union's regard for human liberties as guaranteed both in the nation's new constitution and in the Helsinki agreement on European security.

The fair's morning sessions were closed to the public, but this afternoon, when the doors were opened, thousands of Russians trouped inside to gawk at and fondle books from thousands of miles from here. Books on karate, on modern painting and sculpture, and lavishly illustrated volumes of science and nature studies captivated the crowds.

Tass recently noted that among the publishers here were several from Israel, with which the Soviet union does not have diplomatic relations. The israeli booths were jammed with people, and many were not browsing, but reading deeply.

The seizure of the books - all offewell as of four publishers' catalogues, seems certain to add to a debate now under way among many American publishing houses. The debate centers on whether publishers should participate in an exhibition in a country where some writers have been persecuted, imprisoned or exiled, and in which certain names, ideas or pictures common in Western culture may be forbidden.

In addition to Orwell's books, offered by the New American Library in paperback editions, these other books and catalogs were banned:

Books -Three volumes of a series for young readers on ethnic Americans, entitled "Jews in America," "Ukrainians in America" and "Czechs-Slovaks in America," offered by the Lerner Publications Co. of Minneapolis: "The Secret police in Lenin's Russia," by Lennard D. Gerson, for Temple University Press; "The Sino-Soviet Conflict and East Europe," by jacques Levesque, published in French by the University of Montreal: and "Images of an Era, The American Poster, 1945-75" by M.I.T. Press.

Catalogs - Those of The Oxford University Press for fall 1977, which includes a one-paragraph descriotion of a book entitled "The Social and Politial Thought of Leon Trotsky"; of British publisher Jonathan Cape, which includes mention of "The Ivankiad" by suppressed Soviet dissident writer Vladimir Volnovitch, who lives here; British publisher Andre Deutsch, which contains a reference to a book of comparative Soviet government studies: and of the American Association of University Publishers, which lists university press books available for secondary school libraries.

The protests were lodged by Martin Levin, president of the Times-Mirror Co., publishers of New American Library's Orwell titles; and Chester kerr of the Yale university Press. He is here as chon of University Presses, which represents 71 universities exhibiting books here.

They were told by Boris Stukalin, chairman of the Soviet State Committee on Publishing, that although it is a customs matter Stukalin will "look into it" for them. The principal purpose of the long-hour meeting with Stuklin was to discuss Soviet-American publishing agreements. In a sense, the fact that a meeting originally called to talk about business matters eas expanded to include questions of censorship illustrates the dual nature, or perhaps dual impulses, of the American presence here.

There are more than two dozen American companies here. Many of their sales representatives now in Moscow attended a New York meeting last month of the Freedom to Publish Committee of the American Publishers Associaton, in which various publishers' representatives debated the question of Soviet freedoms.

Some people at that meeting adovcated attending the fair for business reasons, to seek out new markets and exchanges in a businesslike frame of relations. Others advocated an activist, role by the American representatives, urging them to speak out on human rights and to press their views of the need for dissent and the right to speak one's conscience.

That debate ended without substantial resolution, and that duality was evident here today. A number of sales representatives seemed mildly interested in the book seizures, but it was not an emotional issue. Most were curious about the Russians and pleased that the exhibition halls were crowded with people.