Ronald Ellis was formally charged yesterday with the slayings of his wife and five other persons after he had ended eight days as a fugitive by unexpectedly surrendering to the FBI at its downtown headquarters.

Ellis, exhausted, fighting back tears and at times shaking his head from side to side, stood before a court official in the Prince George's County courthouse and was formally charged with six counts of murder in connection with the mass slaying in his home May 2.

In interviews with FBI officials, Ellis, who had disappeared after fleeing to Chicago the day of the slayings, said that he had traveled 4,000 miles since he left the Washington area, but would say little else to investigators, according to law enforcement sources.

Ellis, 34, was described by his attorney, R. Kenneth Mundy, as "quite worried" and particularly concerned about his only surviving daughter, 15-year-old Tracey Ellis. Mundy, a prominent D.C. criminal defense lawyer, accompanied Ellis throughout a day of routine court appearances involving various charges against him.

Mundy announced at the end of the day that his client will plead not guilty to the murder charges stemming from the shootings of Ellis' wife, Ingrid, a D.C. police sergeant, their daughters, 12-year-old Tammy and 4-year-old Monica, and three others in their Camp Springs home. Ingrid Ellis was killed with a handgun, and the others were herded into the corner of a bedroom in the large split-levil house and killed with shotgun blasts.

Ellis, who had telephoned his father last Thursday and told him he wanted to surrender, turned himself in at 11:55 p.m. Sunday to employes at the FBI's main "escort desk" at the courtyard entrance to the agency's headquarters. Ellis was accompanied by his father, John D. Ellis Jr., and a sister.

Ellis, a pressman at a Silver Spring printing plant, allegedly fled to Fairfax County after the shootings and forced a female acquaintance and her young son to drive with him to Chicago. The two escaped when Ellis allegedly got out of the car, leaving the keys in the ignition, at a highway rest stop just inside the Chicago city limits. He disappeared, and a nationwide alert by law enforcement authorities failed to produce any leads.

Ellis, however, called his father, who was staying with relatives in a Maryland suburb, at least twice since May 2. In one call, last Thursday morning, John Ellis told his son in urgent tones: "Get in touch with the FBI. Period. Not those local yokels."

Shortly before midnight Sunday, Ronald Ellis did just that. He walked into the J. Edgar Hoover Building's courtyard entrance to a desk where visitors are normally received and told FBI employes there that he wanted to surrender. A night duty agent, Gerald G. Shockley, was summond. At 12:15 a.m., after Ellis' identity was confirmed, he was arrested and formally charged with unlawful flight to avoid prosecution.

While he was being questioned, lawyers from Mundy's office were summoned, apparently by Ellis' family, and one of them, Robert Mance, remained with Ellis throughout the night, according to law-enforcement sources.

Shortly after 1 a.m., agents from the FBI's Washington Field office came to pick him up and transferred him in handcuffs to their office at Buzzard Point. The administrative personnel at the main headquarters do not normally interrogate suspects.

While at Buzzard Point, agents questioned Ellis, who according to sources appeared cautious, well prepared and composed. He refused to comment on the charges against him or say where he had been since the May 2 slayings. Through the night, he ate a doughnut, drank a soft drink and some coffee and slept periodically.

At 8:30 a.m. yesterday he was taken by FBI officials to the central cellblock of the District police, where he was fingerprinted and photographed and was then turned over to officials of the U.S. District Court.

Because Ellis allegedly fled from the state of Maryland, where he was wanted for murder, federal authorities had charged him with unlawful flight to avoid prosecution. Those charges provide a formal way for the FBI to enter the investigation, and after the arrest. Ellis had to be taken before a federal magistrate to answer those charges.

His first public appearance, therefore, came at about 10 a.m. yesterday before U.S. Magistrate Jean Dwyer in a small wood-paneled room in federal court. Ellis, wearing a navy-blue sweat jacket, faded jeans and Nike running shoes, stood before Dwyer, his eyes downcast and his arms dangling limply at his sides.

Dwyer dismissed the federal unlawful flight charge after prosecutors described it as an unnecessary formality with Ellis in custody on murder charges.

Besides acknowledging that he understood his rights, Ellis' only words during the brief hearing were: "I'd like to speak to Mr. Mundy in private. That's all I want." Mundy said later that he did speak with Ellis privately for about 15 minutes.

After the federal hearing, Ellis was taken to D.C. Superior Court, where he was formally charged as a fugitive. Although he had the right to fight extradition to Maryland on the murder charges, Mundy told Judge Samuel Block that his client chose not to do so, and Prince George's sheriff's deputies immediately took him to Upper Marlboro.

There, in the basement of the courthouse, Ellis, wanted in one of the most violent slayings in county history, stood before a small glass window, with lawyer Mance and sheriff's deputies around him. The court official behind the window told him he was charged with six counts of first-degree murder.

Throughout the day Ellis' father, his brother and one of his five sisters followed him from courtroom to courtroom. His mother, Mary Ellis, who has returned to Shelby, N.C., where she and her husband retired two years ago, said her son "needs all the support he can get, and I'm going to give it to him."

She said she is glad Ellis surrendered. "I feel relieved he's not out in the world. I feared he'd be blown apart. It'll be many nights before I can sleep," she said.