Henry Hearns, a younger brother of Thomas Hearns, was held in the fatal shooting of a female friend at a home owned by the boxer, station WDIV-TV in Detroit reported today.

The police in this Detroit suburb refused to identify either the 22-year-old suspect or the victim, described as in her 20's, until an arraignment Monday. But the police said that the woman was known to the Hearns family. Another Detroit station, WXYZ-TV, identified the victim as Nancy Barile, 20, a friend of Henry Hearns.

Handlers for Thomas Hearns, who is in Las Vegas preparing for Monday night's title bout against Sugar Ray Leonard, said Hearns would fight as scheduled.

Several people at Hearns's home went to the police department to report the shooting late Saturday night, and the suspect was arrested about 1 A.M. Sunday, said Officer Gary Conat, a department spokesman.

The suspect had been scheduled for arraignment on an open murder charge at 10 A.M. today in 46th District Court in Southfield, Police Cpl. Peter Ponzetti said. That hearing was delayed because a formal warrant had not been issued by the Oakland County Prosecutor's Office, Conat said.

The victim's body was found in a bedroom of Hearns's home. She had been shot once in the head, and a handgun was recovered at the scene, Police Lieut. Lloyd Collins said.

Conat said the shooting stemmed from a ''domestic situation, not a social situation'' but would not comment on a possible motive. The police did not immediately know to whom the handgun was registered, he said. Six Are Questioned

The suspect was one of six people questioned after the shooting, the police said. Henry Hearns had been at the police station accompanied by a Detroit attorney, Neil Fink, after the shooting, but officials wouldn't say if he was among those questioned.

Prentiss Byrd, an aide in Thomas Hearns's camp, said Hearns was aware of the shooting and would proceed with the fight. He quoted Hearns as saying: ''I've got to do what I've got to do. A lot of people worked to make this fight happen.''

The promoter Bob Arum said from Las Vegas that he understood the home where the shooting occurred was one of four owned by Thomas Hearns and not the fighter's actual residence. The police said they could not comment on Arum's statement.