Rep. John E. Moss (D-Calif.), a consumer champion and vigorous watchdog of governmernt spending is suing a Fairfax County housewife for $500,000, claiming that an automobile accident involving the woman caused him injuries that led to his early retirement from Congress.

Moss, who announced last January he would not seek reelection testified in U.S. District Court in Alexandria that the accident last year with Alice E. Graham, 56, caused him to lose about $6,000 a year in retire two years earlier than planned.

Sometimes raising his voice in anger at questions from Graham's attorney, sometimes arguing with the attroneys, the grim-faced Moss, a 26 year veteran of the House testified that the "gnawing aching" of his right shoulder, allegedly resulting from the accident, forced him at times to miss roll calls and committee meetings and forgo his reelection plans.

Moss, 63, leaned forward in the witness stand and answered loudly on several occasions. When asked why his wife was driving the car at the time of the accident, Moss replied "She 's a hell of a lot better driver than I am."

He also became angry when Graham's attorney, Fred Alexander, asked him if four of his staff members had investigated the accident afterward.

"I did not cause any member of my staff to investigate." Moss replied, enunciating each word carefully in a loud voice." "I had members of my staff volunteer to investigate this."

The climax of the shouting matches scattered through Moss' testimony occurred when Alexander asked Moss if he had announced his retirement in order to escape making additional financial disclosures required by a new law.

"That had nothing to do with it," Moss shouted. Moss, one of his lawyers and Alexander all began yelling at each othe while Judge Richard B. Kellam, of Norfolk, with his mouth open and finger wagging at the men, seemed momentarily unable to speak.

Much of the testimony yesterday hinged on Moss' claims of severe shoulder and neck pain from the accident, injuriesthat a Navy doctor said on the stand were "partly age-related and could be accelerated by injury."

Moss testified that he could not recall suffering from such pain before the accident, although medical records from Bethesda Naval Hospital, introduced by Alexander, showed that Moss had been treated for similar afflictions in 1963, 1965 and 1967.

Dr. Thomas Bem, whose testimony was introduced in a deposition, said that Moss, chairman of a House oversight committee, visited government physicians for consultation or physical therapy for his shoulder and neck 73 times after the accident on April 30, 1977.

Dr. Berton Slemmons, a Naval orthopedic physician, testified that Moss has had an underlying condition of osteoarthritis and that his neck pain could have been caused by previous problems. "Prior to the accident he probably was having some symptoms of neck problems."

Slemmons said he gave Moss neck exercises, but that Moss later told him he wasn't doing them regularly. Moss' attorney, Richard Lewis, jumped up and shouted. "No, that's no right. He said he did them only in the shower."

In addition to other afflictions, Moss suffers from cervical arthrites, Slemmons said, which he said means that the source of pains in different parts of his body could be the age-related degenerationof vertebrae in the spine.

According to testimony, the accident occurred at the intersection of St. Asaph and Queen streets in Old Town as Moss and his wife Jean were headed home after an outing in the Alexandria area.

Moss said the couple had stopped for a red light. When the light changed, Moss said, the Mosses entered the intersection and saw Graham's 1967 Cehvrolet Belair "coming from the right and it was coming like a bat out of hell."

"All I know, I was violently pushed and I seemed to be driven downward in the seat," Moss testified.

Graham has not yet testified, but Alexander, in his opening statement, said Grahaham had the green light at the intersection.

Moss, who earns $57,500 as a congressman, said he will receive only $32.70 a year in retirement compared to the $38.436 he would have received had he remained in office two more years.

Moss said he has no stocks or bonds and a few U.S Treasury notes and has no immediate plans for employment after he retires. "I am not a wealthy man," he said.