Betty Watt Brooks, 80, a retired biologist and administrator with the U.S. Public Health Service, died Thursday at a nursing home in Richmond. She had a lung ailment.

Dr. Brooks began here career with the PHS here in 1951 as a research analyst in the division of state grants. At her retirement in 1970, she was executive secretary and public health analyst of the office of grants and contracts in the agency's health services and mental health administration.

She was born in Wellesley, Mass. She earned bachelor's and master's degrees at Wellesley College and a doctorate in biology at the University of Pittsburgh. She worked at the Carnegie Institute in Cold Spring Harbor, N.Y., and the Carnegie Institute in Pittsburgh, taught at the Pennsylvania College for Women, and worked at the Department of Commerce and as a technical editor for the Field Information Agnecy in Germany before joining the Public Health Service.

Dr. Brooks had lived in Washington Grove, Md., until about five years ago, when she moved to Richmond.

She was a member of the Montgomery County Mental Association, and a former treasurer of the Montgomery County Commission for Preserving Town Records.

She was a member of the American Public Health Association, the American Academy of Political and Social Scientists, and other professional groups. She was a member of the National Association of Retired Federal Employees fo the American Association of Retired Persons.

Dr. Brooks was the widow of Dr. Stanley Truman Brooks, a zoologist, whom she married in 1927. He died in 1958.

Her survivors include two daughters, Mrs. Clyde Kenyon, of Richmond, and Mrs. Richard E. Andersen, of Washington Grove, a son, Stanley Hunter W. Brooks, of Powhatan County, Va., and five grandchildren.