Top leaders of eight mainline Protestant denominations and the National Council of Churches transformed the nation's capital yesterday into Good Friday stations of the cross, in which they marched and prayed and preached against U.S. military aid to El Salvador.

"We protest the policy of seeking military solutions to human problems," said the Rev. Arie R. Brouwer, general secretary of the Reformed Church in America. Speaking at noon to about 250 persons huddled under umbrellas in Layayette Square across from the White House, Brouwer said that the Reagan administration has refused to discuss the El Salvador situation with Protestant leaders. "Our written appeals have passed before blinded eyes," he said. "Our requests for meetings have fallen on deafened ears," he said.

Even as he spoke, Vice Peresident Bush stepped inconspicuously from his limousine into St. John's Episcopal Church on the other side of the Square, for a more traditional Good Friday service. Like the vice president, Christians here and throughout the world marked Good Friday, the day on which Christ was put to death, with services beginning at noon -- the hour when His crucifixion began -- or last night.

In Roman Catholic tradition, Good Friday is the time to make the stations of the cross, the symbolic reenactment leading to his crucifixion. Yesterday's prayer and protest march led by the Protestant leaders was an adaptation of that practice, with the White House, the State Department, the Organization of American States and the World Bank, in the church leader's view, as the contemporary sources of suffering.

The El Salvador problem is the first issue since the Vietnam war to send top Protestant leaders into the streets. Despite their hymns and somber prayers, their anger over what they termed U.S. complicity in the suffering of the people in that country was never far from the surface.

"As the crucifixion of our Lord depended on the imperial power of Rome," Brouwer said, "so the terror in El Salvador depends on the power of our government. We are here to say 'Stop' to our government."

In response to a question about the appropriateness of their protest on Good Friday, the Rev. Avery Post, president of the United Church of Christ, said that in expressing "solidarity with the suffering people of El Salvador . . . we believe that what we are doing today is exactly what God wants us to do," because Good Friday has a special significance for suffering and poor people.

The Roman Catholic Church in this country has been particularly visable in opposition to military aid to El Salvaodr, but except for a handful of nuns and some Catholic lay people, yesterday's vigial was planned as a Protestant event "to make it very clear that El Salvador is not just a Catholic issue," sid the Rev. Dr. William 'howard, president of the National Council of Churches. The Protestant leaders yesterday paid lavish tribute to Catholic leaders in El Salvador, several of whom have been martyred.

A dozen clergymen and women in their long black pulpit robes took turns yesterday carrying a rough wooden cross along Pennsylvania Avenue and down 19th Street. The neatly dressed worshippers, who ranged in age from young children in strollers to senior citizens, carried only a few handmade palcards and tourists and others in the lunch hour crowd wondered aloud about the purpose of the march.