A. Philip Randolph, founder of the first major black labor union in the United States and a major figure in the civil rights movement, died yesterday at his home in New York City. He was 90.

The cause of death was not disclosed, but Mr. Randolph had heart ailments and high blood pressure.

Mr. Randolph was one of the most original as well as one of the most effective advocates of racial equality in this country in modern times. At a time when American society was almost entirely segregated, he was the first to use economic power to better the lot of blacks. He began in one of the few industries to which blacks were relegated-and in which they could make their economic power felt.

In 1925, he organized the Brotherhood of Sleeping Car Porters. It was the first black union granted a charter by the American Federation of Labor. In 1955, when the AFL merged with the Congress of Industrial Organizations to form the AFL-CIO, Mr. Randolph was instrumental in persuading it to ban discrimination in unions. In 1957, he became a vice president of the AFL-CIO.

His horizons were broader than the union he founded. He was a major force in opening war industries in World War II to black workers in persuading President Harry S. Truman to end segregation in the armed services after the draft was reinstituted in 1948 during the first days of the Cold War.

He was an organizer of no less than five marches on Washington, including the massive demonstration led by the late Dr. Martin Luther King in August, 1963. That march was a factor in the passage of the 1964 Civil Rights Act. The legislation outlawed discrimination in public places of accommodation, employment and unions.

It thus embodied the goals for which Mr. Randolph strived for most of his life.

Among his other concerns was segregation in the nation's school systems, and his death occurred on the eve of the 25th anninversary of the U.S. Supreme Court's historic decision in the Brown vs. Board of Education case which outlawed the separate-but-equal standard which had prevailed in many of the nation's public school systems.

The 1963 march was the last in which mr. Randolph played a role. The first was in 1941, and its purpose was to persuade President Franklin D. Roosevelt to end discrimination against black workers in war industries. The president acted and the march proved unnecessary.

Mr. Randolph's other marches were a Pilgrimage of Prayer in 1957 and Youth for Integrated Schools in 1958 and 1959.

A guiding principle throughout Mr. Randolph's life was the achievement of change through peaceful means. Some civil rights leaders of the militant 1960s criticized him for his patience and his willingness to go forward slowly, but he never abandoned his faith in these tactics.

In a 1973 interview he said he drew his inspiration from Mahatma Gandhi, the great Indian leader who employed civil disobedience to attain his country's independence from Britain.

"I think that perhaps in my work I was distinguished more for my championing of the philosophy and principes of Ghandhisim than I was, at times, fro trade unionism," he said.

Another influence in his life, he said, was the example of his father, a minister in Florida.

'My father was happy about my nonviolence stand," he said. "He didn't want to feel that his son was going around the coutnry urging black people to rise up against white people and use physcial force."

Mr. Randolph planned the 1963 march with Bayard Rustin, now head of the A. Philip Randolph Institute, an organization devoted to increasding voter registration among blacks and helping to improve econimic opportunities for them, particularly at the management level.

In announcing Mr. Randolph's death, Rustin said, "No other living American has done more to seek justice for all the poor, the working classes and the minorities in our society and around the world than has A. Philip Randolph."

Asa Philip Randolph was born on April 15, 1889, in Crescent City, Fla. His father, James William Randolph, supplemented the small income he derived from his preaching in the African Methodist Church by working as a tailor. His son contributed to the family income by working in a grocery.

After finishing high school in Jacksonville, Fla., the young Randolph moved to New York City. He became an elevator operator and eventually a porter on a railroad. He was fired for his early efforts to organize his fellow workers.

In 1971, Mr. Randolph organized a small group of elevator operators. He began his work among railroad porters in 1925, when he became convinced that the Pullman Co. was exploiting a large, relatively homogenous group of black workers.

The Pullman Co. fought back. Many porters lost their jobs for joining the nascent labor organization. When Mr. Randolph threatened a strike, other railroad union refused to support the Sleeping Car Porters.

Success did not come until after the passage of the Railroad Labor Act in 1934. In 1937, Mr. Randolph signed a contract with the Pullman Co.

He signed in 1968 as president of the union he had founded.

Mr. Randolph'wife, Lucille, died in 1963.

At the time of his death, he still lived in the apartment in the Harlem section of New York where he spent much of his life.

He left no immediate family. CAPTION: Picture, A. Philip Randolph, civil rights leader speaking in Washington in 1963, AP