Dr. Julius B. Richmond, professor of Child Psychology and Human Development, has accepted President Carter's nomination as assistant secretary of Health, Education and Welfare, a Medical School spokesman said yesterday.

Richmond, who is currently a member of the President's Commission on Mental Health, is attending a convention of the American Pediatrics Association in California and could not be reached for comment yesterday.

Sources at the Med School said Richmond refused the post in January when Carter first offered it to him.

Diana K. Rock, a spokesman for the White House personnel office, said yesterday the Federal Bureau of Investigation (FBI) is currently conducting the required security check on Richmond.

If confirmed, Richmond will be able to maintain his position on the mental health commission in addition to his assistant secretaryship, Rock added.

If the FBI investigation reveals no problems in Richmond's record, President Carter will forward the nomination to the Senate for committee hearings and confirmation, Rock said.

The Washington Post reported Thursday that Carter would soon nominate Richmond and that four other potential nominees, including Dr. Charles N. Sanders, director of Massachusetts General Hospital, had refused the nomination.

HEW officials, including Hale Champion, former Harvard vice president for financial affairs, refused to comment on the status of Richmond's nomination, but Sanford Winston, chief press officer for HEW, said "published reports have not been too far from the truth."

Spokesmen for HEW said earlier that Howard H. Hiatt, dean of the School of Public Health, had been considered for the position.

Hiatt said yesterday, "Richmond is one of the most accomplished physicians in the country with experience in public policy," adding, "This is a superb appointment."

David S. Weiner, director-designate of the Children's Medical Center, said "Richmond shows a broad, in-depth understanding of health-care systems" and will provide valuable advice to HEW Secretary Joseph A. Califano on health care financing and administration.

Shrinks Say Yes

Judith Weitz, health specialist for the National Children's Defense Fund, said yesterday Richmond is "a terrific appointment from our perspective," adding that Richmond commands great respect among child psychiatrists.