A 26-year-old Northwest Washington man was arrested yesterday and charged with homicide in the death of a former girlfriend whose disputed testimony at a 1979 hearing in Montgomery County apparently helped free him of a murder charge he faced there.

David Leander Stratmon Jr., of 7573 Alaska Ave. NW, was arrested at his home about 4 p.m. and charged in the death of Stephanie Walker, a 22-year-old Montgomery County woman whose body was found at the Alaska Avenue address. Investigators said there were indications that she died of a beating, but that they would have to await the outcome of an autopsy to be certain.

Stratmon had been arrested Jan. 28, 1979 and charged with murder in the death of Claire Levy, a 24-year-old Silver Spring woman who was found strangled in her bed early that morning.

Charges against him were dropped, however, after a preliminary hearing at which testimony was heard from Walker, who was found dead yesterday.

Walker was later charged with perjury in connection with her testimony and was found guilty in November 1979, on four counts of obstruction of justice. She reportedly was given probation in connection with the conviction. No new charges were ever brought against Stratmon in the case.

One of those who testified at Walker's perjury trial was Vivian Levy, 23, of Providence, R.I., the sister of the woman who was found strangled in Silver Spring. Only hours after Vivian Levy had testified, her body was found in a motel room in Rockville. The state medical examiner's office ruled that she had died of a drug overdose.

Stratmon, who is unemployed, and Walker, who had been studying data processing, reportedly had been acquainted for about three years.

Walker was "a very nice girl . . . one of the nicest persons I ever met," Stratmon's father said last night. She and Stratmon had a son, who is about 2 years old, the senior Stratmon said.

Few details about yesterday's incident were immediately available.

Police said Walker had a cut on the head when he was found, but they gave no information about other possible injuries. They said they knew of no motive in the death.

Neighbors said they had not seen or heard anything unusual.