Arthur W. Powell, 57, a government accountant for more than 20 years and an official of Georgetown University, died Sunday at Washington Adventist Hospital. He had suffered from a heart ailment.

Mr. Powell began his government career with the old Atomic Energy Commission in Paducah, Ky. He later was transferred to Cincinnati, and in 1961 switched to the Cleveland office of the National Aeronautics and Space Administration. He was transferred to Washington in 1963, and served as the agency's assistant director of financial management and construction audits.

In 1969, Mr. Powell joined the Department of Health, Education and Welfare. There he helped put into operation a system by which HEW made grants available to states through letters-of-credit.

Under the letter-of-credit system, HEW guarantees payment of a grant to a state. The state then submits vouchers through a federal Reserve Bank as it uses the money. The advantage to the federal government is that it makes payments only as the money is used rather than making an initial payment for the entire grant. The system has been credited with easing the federal government's cash-flow difficulties.

Mr. Powell retired from HEW in 1975. A year later, he became director of facilities control at Georgetown University, a job he held at the time of his death.

Mr. Powell also had taught accounting at Montgomery College in Rockville. He was a member of the Montgomery-Prince George's chapter of the Association of Government Accountants and of the Bethesda United Church of Christ.

Mr. Powell was born in Morgantown, W. Va. He won a Bronze Star while serving in the Army in the South Pacific during World War II. He later graduated from Western Kentucky University at Bowling Green, Ky., with a degree in commerce. He specialized in accounting there.

Survivors include his wife, Gay, of the home in Rockvile, and two sons, Arthur W. Jr., also of the home, and Robert, of Alexandria.

The family suggests that expressions of sympathy be in th form of contributions to the Montgomery County chapter of the American Heart Association.