El Salvador's ranking Roman Catholic leader has appealed to members of Congress to pass legislation that would end U.S. deportation of Salvadorans fleeing the six-year civil war.

Archbishop Arturo Rivera y Damas of San Salvador, writing to "Honorable Members of Congress," asked them to "double your efforts against the deportation of Salvadoran refugees."

He called for passage of an immigration bill that, among other features, would suspend for two years deportation of Salvadorans in this country illegally. The bill has cleared the Senate, but House hearings have not been completed.

Writing "in the name of . . . Christian love," the archbishop said that "to return the persecuted to the source, the origin, the cause of his suffering is an act of injustice in the eyes of Christian love."

The Reagan administration contends that the Salvadorans come here for economic, not political, reasons.

The archbishop's letter contradicts testimony by Assistant Secretary of State Elliott Abrams on April 22 that quoted the archbishop as denying that there was a "pattern of persecution" of deportees.

Dated Nov. 15, the letter was sent to the Central American Refugee Center here, which transmitted it to Rep. John Joseph Moakley (D-Mass.), cosponsor of the pending immigration bill. Moakley made the letter public Tuesday.

Moakley called the letter "a major boost" to the bill he and Sen. Dennis DeConcini (D-Ariz.) introduced two years ago.

Leaders of the U.S. Roman Catholic hierarchy are out of the country attending the Synod of Bishops in Rome and were not immediately available for comment.

Staff members at the U.S. Catholic Conference here said church leaders have mixed feelings about the lobbying of Rivera y Damas for a specific bill, albeit one that U.S. bishops have said they support.