Former Premier Cyrille Adoula of the Democratic Republic of the Congo, now Zaire, died Wednesday at Lausanne, Switzerland,after a long illness, the Embassy of Zaire announced here.

Mr. Adoula, who was 56, was an associate of Patrice Lumumba, the first premier of the Congo after it gained independence from Belgium in 1960. He became head of the governement in 1961, the year Lumumba was murdered, and retained the post until 1964. Mr. Adoula also was an associate of Gen. Mobutu Sese Seko, now the president of Zaire, and served the Mobutu government as foreign minister from 1969 to until he was fired in 1970.

Mr. Adoula's years as premier were marked by efforts to deep his country intact in the face of tribal separatism and pro-Soviet infiltration. The late Moise Tshombe tried to lead copper-rich Katanga, now Shaba, the scene of bloody fighting in recent days, out of the Congo, which officially changed its name to Zaire on Oct. 27, 1971.

From 1966 to 1969, Mr. Adoula was the Congo's ambassador in Washington. He had served as ambassador to Belgium from 1964 to 1966.

The son of a dockworker in Leopoldville, now Kinshasa, Mr. Adoula worked in a bank for several years until he joined the trade union movement in 1956. He became general secretary of the General Federation of Workers, which had backing of Belgium before independence.