Navy Capt. Alexander G.B. Grosvenor, 50, commanding officer of the Annapolis Naval Station since 1975, and commodore of the Naval Academy sailing squadron, died of cancer Friday at the Naval Hospital in Annapolis.

Capt. Grosvenor served two combat tours in the Korean and Vietnam wars as a Navy pilot.

A native of Washington, he was 1950 graduate of the Naval Academy at Annapolis, and earned his aviator's wings at Pensacola in 1952.

During the Korean conflict he served aboard the aircraft carriers USS Yorktown and USS Essex.

He then was flag lieutenant to the commander of the Mediterranean Fleet and head of the fighter aircraft test branch of the Navy's test pilot school at Patuxent River, Md.

During the Vietnam war Capt. Grosvenor served aboard the carrier USS Coral Sea and USS Ranger, and was commanding officer of Fighter Squadron 21.

From 1969 to 1971, he was executive officer of the carrier USS Kitty Hawk, and then was transferred to the Office of the Secretary of Defense, where he served until 1973.

That year he was named director of the service test division at Patuxent River Naval Air Test Center, a post he held until being named commanding officer of Annapolis Naval Station.

Capt. Grosvenor held a number of decorations, including the Distinguished Flying Cross, the Navy Commendation Medal with Combat "V" the Bronze Star and Air Medal.

He is survived by his wife, Marcia, and two daughters, pamela and Sandra, all of the home in Annapolis: his mother, Helen R. Grosvenor, of North Palm Beach, Fla.; his father, Dr. Melville B. Grosvenor, of Bethesda; a brother, Gilbert M., editor of the National Geographic Magazine, of McLean, and a sister, Mrs. Richard Lemmerman, of Manchester, Mass.

The family suggests that expressions of sympathy may be in the form of contributions to the American Cancer Society or the Naval Academy Sailing Foundation.