Ralph P. Joy, 52, an official of the National Education Association for 15 years, died of a heart ailment Wednesday in a hotel in Rosemont, Ill. He was in Illinois on Association business.

Mr. Joy came to Washington and joined the staff of the NEA's urban project as a field representative. He rose to the post of director of the Association's membership division and then became first director of the NEA's Leadership Training Academy in 1969. He held this post at the time of his death.

He spent part of a six-month sabbatical from the Association in 1976 to 1977 as a counselor to prisoners in the District of Columbia's Lorton Reformatory. He also had been active in Fellowship House, a religious organization founded by former Sen. Harold Hughes (D-Iowa).

Mr. Joy was a native of Des Moines, Iowa, and was a 1950 fine arts graduate of the University of Iowa. He was a speech and drama teacher in Iowa schools and worked for a Des Moines radio station before becoming a staff director of KDPS-TV in Des Moines in 1957. KDPS was one of the early public television stations.

He then worked as executive secretary of the Des Moines Education Association from 1960 to 1964. He also had been acting executive director of the Iowa State Education Association for a short time this past year.

Mr. Joy was a resident of Falls Church.

He is survived by his wife, Harriet, and a son, Daniel, both of Falls Church; three other sons, Timothy, of Gray, Me., Mark, of Richmond, and Anthony, of Manchester, N.H.; a daughter, Carol, of Richmond; his father, Maxwell, and a sister, Nancy Borg, both of Des Moines, and three grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Heart Association Fund Memorial, 2233 Wisconsin Ave., Washington.