A drama of political and national passions will be played out today over President Carter's decision to return to Hungary the symbol of its nationhood - the golden Crown of St. Stephen.

At a House hearing this morning, some Hungarian-Americans are expected to offer lavish praise of the decision as a recognition of improved human rights in the Eastern European nation, and others are expected to protest fervently that the return would legitimize a still-repressive regime.

A source with the International Relations Subcommittee on Europe and the Middle East, which called the hearing after Carter's decision became known last week, said yesterday that subcommittee members will not vote on a bill designed to stop the return.

"All we're doing is providing a forum for people to lett off steam," he said.

However, in an effort to change Carter's mind, Rep. Mary Rose Oakar (D-Ohio) called First Lady Rosalynn Carter yesterday to seek a White House meeting. As a result, Vice President Mondale agreed to meet this afternoon with Oskar, three other members of Congress and a dozen ethnic leaders, including Geno Baroni, assistant secretary of housing and urban development.

Several hundred Hungarian-Americans, some in folk garb, are planning a demonstratation on the steps of the Capitol before today's 11 a.m. House hearing.

Meanwhile, the administration is going ahead with plans for Secretary of State Cyrus R. Vance to head an American delegation that would deliver the ancient crown and other regalia to the Hungarian people in early December.

The date has not been set, but officials are considering the weekends just before and after Vance is scheduled to attend a NATO ministerial conference in Brussels Dec. 7 and 8.

Enameled and richly decorated with emeralds, rubies and miniature religious scenes, the Byzantine-style crown itself has long been the center of an art historians' dispute. Tradition holds that it was given to Hungary's first king, stephen, for his coronation in the year 1000 by Pople Sylvester II.

But some historians contend that the top part of the crown, the older part, dates to nearly 100 years after Stephen died in 1038.

Regardless of its origin, the crown is intimately linked to Stephen, who was canonized by the Catholic Church in 1083 largely because he made Hungary not only a Christian nation but a Roman Catholic instead of a Greek Orthodox nation.

The relic, used in the coronation of every Hungarian monarch through that King Karl in 1916, was removed from Budapest by the Crown Guard in October, 1944, as the battleline between the Nazis and Soviets edged toward the capital.

In 1945 it was turned over to American military forces in Austria for safekeeping. It was kept in U.S. custody in West Germany until the early 1950s, when it has remained ever since along with Hungary's orb, scepter, sword, and coronation robe.

After the end of the repressive Hapsburg dynasty, Hungary had a riged right-wing regime, gascist rule, a brief freely elected republican government, and the Communist takeover of 1947 followed by the famed 1956 "freedom fighters" uprising that was crushed with the aid of Soviet troops and tanks. Janos Kadar was installed by the Soviets as Hungary's new leader.

In recent years he has liberalized the nation to a decree greater than that of other Warsaw Pact countries. Compared with other Eastern Europeans, Hungarians have a good deal of religious, speech, and economic freedom.

U.S.-Hungarian relations have improved markedly since the 1966 decision to exchange ambassadors. In 1970 Hungary lifted travel restrictions on U.S. embassy personnel. The next year Jozsef Cardinal Mindszenty, a fervent anti-Communist who had been granted asylum in the U.S. embassy in Budapest, left the country, thus eliminating a source of friction between the two governments.

In the next two years Hungary agreed to protect U.S. citizens visiting there and to compensate U.S. citizens who lost property through nationalization.

Last December Hungary paid off the last of its World War I debt to this country, and in April the two nations signed a cultural and scientific exchange agreement. Further moves toward normal relations, including a U.S. grant of "most favored nation" trading status, have been hampered by U.S. possession of the crown, which Hungary has long wanted back.

In may, top government officials in several departments began studying the crown issue. This summer Vance and other members of Carter's Policy Review Committee recommended that the crown be returned.

The President agreed in September and on Oct. 1 Vance met with Hungary's foreign minister. Frigyes Puja, at the United Nations General Assembly in New York. It is understood that Hungary has agreed to put it on public display and not to place restrictions on Hungarians or foreigners who want to see it.

Rep. Ozkar, who represents a large Hungarian-American constituency in Cleveland, said in an interview that the Kadar regime is "the antithesis of human rights. Do you want to legitimize a Communist, atheistic government by giving it a sacred religious symbol?"

But Ferene Nagy, the elected prime minister who was overthrown by the Communists in 1947 and who now lives in Herndon, Va., said he supports the Carter decision.

"The legitimacy of the regime, of which I consider myself the number one enemy, was recognized by the United States long ago," he said. "The crown will be given back to the regime as such but to the Hungarian people, and it will help provide them with the will to survive."

Andras H. Pogany, a spokesman for the Coordinating Committee of Hungarian Organizations in North American, and president of the World Federation of Hungarian Freedom Fighters, said Carter promised during the election campaign last year not to do anything about the crown until he had consulted with the coordinating committee, "We had a presidential promise, but it's just in the air," Pogany said.