Alexander Stewart Meloy, 70, a former engineering officer for the old U.S. Maritime Service and the Department of Commerce's Maritime Administration, died of cancer Jan. 23 at a hospital near Tuson. He lived in Green Valley, Ariz.

Mr. Meloy served in the Navy's Submarine Service from 1931 to 1935. In 1942, he became a marine engineering instructor for the old Maritime Service and later served as a engineering offier aboard U.S. merchant ships.

Following World War II, Mr. Meloy transferred to the U.S. Maritime Station at Alameda, Calif., where he was supervisor of training and station operations.

In 1958, he became safety officer for the West Coast U.S. Reserve Fleet for Commerce's Maritime Administration. He transferred to Washington in 1961, when he became safety officer for the entire Reserve Fleet.

He returned to California, in 1969, as senior fleet engineer for the U.S.

Reserve Fleet in Benicia, Calif. He retired in 1972.

Mr. Meloy was a member of an old Washington area family, the Meloys of Lanham. He graduated from old McKinley Technical High School in Washington and attended the University of Maryland.

A former resident of Seabrook, Md., he lived in Napa, Calif., before moving to Green Valley, Ariz., in 1978.

Mr. Meloy served in the Naval Reserve from 1949 until 1969, when he retired as a lieutenant commander.

He was a 33rd degree Mason.

Survivors include his wife, Catherine Todd Meloy of Green Valley; three sons, Robert Todd of Vienna, Alexnader Steuart Jr., of Alamo, Calif., and James Rittenhouse of Simi Valley, Calif., and seven grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.