Gary Ronald Jackson, 26, a decorated veteran of the Vietnam war, was arraigned in D.C. Superior Court yesterday on a charge of voluntary manslaughter in the death of the 2 1/2-year-old daughter of his girl friend.

Judge Bruce S. Mencher ordered Jackson released pending further court action on condition that he commit himself to Walter Reed Army Hospital for psychiatric care. He set a preliminary hearing in the case for Feb. 23.

The victim was identified by D.C. homicide detectives as Rachel Stilts. The D.C. medical examiner's office ruled that she died of "multiple internal injuries" as a result of being beaten. Her death occured Tuesday.

The child was the daughter of Sharon Peterson, who was described in court records as Jackson's girl friend. Jackson lived with them at 829 Barnaby St. SE, police said.

Court records provided this information about Jackson: He spent five years in the Army and received a disability discharge eight months ago; his disability pay was $228 a month; he was unemployed; he was separated from his wife; he had "received gunshot wounds" and had been treated at Walter Reed Army Hospital for "nerves" prior to his discharge.

His widowed mother, Ruth Jackson of Oxon Hill, said in an interview that Jackson had been an Army medic in Vietnam. She said he was awarded the Bronze Star medal for valor and two purple Hearts for wounds he suffered in the war.

"But most of the wound he received was emotional," she said. Mrs. Jackson said her son had had emotional difficulties since boyhood and that the psychiatric care he had received at Walter Reed extended over the six months prior to his discharge.

Since then, she said, he had occasional work at the Veterans Hospital here as a medical attendant.

"I don't believe Gary did the thing he was accused of," Mrs. Jackson said. "I don't think he was capable of it in the first place, and in the second place, he sat there so quietly talking to the police. He simply didn't act quilty. A mother is entitled to believe that."

She said Jackson's relations with his own two children by his marriage were "excellent" and that he also appeared to be very fond of Rachel Stilts.

"This is the second tragedy we've had," Mrs. Jackson said. "On the 30th of January we lost a son through an automoble accident. His name was Terry Richard Jackson and he would have been 25 years old on the 16th of this month. He and Gary were very close and Terry's death had a terrible traumatic effect on Gary.

"We had not had a chance to get over that when this happened."