A Prince George's County man with a history of emotional instability and numerous brushes with the law hanged himself Sunday evening in his cell at Mayland's Patuxent Institution in Jessup, according to an official there.

The man, William Avery Corley, 24, of 2914 73d Ave., Landover, tied one end of a canvas belt that was part of his prison clothing around a grating that covered a light in the wall of his cell, and tied the other end around his neck, according to Robert Johns, the assistant supervisor at Patuxent.

Corley was discovered about 5:30 p.m. Sunday by prison guard Anthony Cuculis, who had seen him five minutes earlier lying on his cot in his cell, Johns said. Cuculis and a rescue squad from Savage, Md., were unable to revive Corley, according to Johns.

Corley's mother, Catherine Corley, said yesterday that she arrived at Patuxent to visit her son at 7:30 p.m., unaware that he was dead. "I had to find out from one of the inmates," she said.

Johns denied that the news of the suicide was withheld from Mrs. Corley. "She was told by one of the inmates before we knew who she was. We comforted her as best we could and offered to get her an ambulance when she started to faint," Johns said. The offer was declined, he said.

Corley had tried to kill himself while incarcerated at Patuxent once before, in August, 1972, by swallowing an overdose of barbiturates, Johns said Corley's record showed. He had been sent to the institution five months before after pleading guilty to a housebreaking charge in Prince George's County.Corley had complained of "homosexual advances" made by other inmates, Johns said.

The court-appointed attorney who represented Corley in the housebreaking matter, Joseph F. McBride, said that Corley had more than 60 scars on his arms resulting from suicide attempts before he entered Patuxent.

While a psychiatric evaluation made at Clifton T. Perkins state mental hospital after Corley's 1971 housebreaking arrest showed Corely to have "antisocial tendencies" and an "inadequate personality," there was no diagnosis that he was suicidal, although the scars were clearly visible on his arms, McBride said.

Corley was paroled from Patuxent on five years of 10-year sentence, John said. On March 15, he was arrested in Roanoake, Va., in connection with an auto theft that day in Fredericksburg, Va., according to Capt. C.C. Brannan of the Frederickburg city police. He was released several days later on $1,000 bond, but failed to appear for trial on April 21, when an arrest warrant was issued, Brennan said.

Corley was arrested for parole violation early last Tuesday at his sister's home in Wheaton, and returned to Patuxent, officials said.