Navy Lt. Cmdr. Mary Ann Cronin, the nurse who struck and killed an Annandale teen-ager in May 1983 as she drove home from a party where she had drunk six beers, has agreed to pay the family of the boy $100,000 as out-of-court settlement of a $1 million civil suit they filed against her.

Cronin's insurance company will pay the family of John R. Svec $45,000 immediately, another $20,000 in five years and a final $35,000 in 10 years.

The Svec family said yesterday they would donate much of the money from the suit to support the efforts of Mothers Against Drunk Driving (MADD), the national anti-drunk driving organization.

"I guess we're satisfied with the amount, but no amount of money could ever replace our son," said Svec's mother, Lynne E. Svec. "We do intend to use much of the money to work against drunk driving through MADD."

Patricia Herzog, of Northern Virginia MADD, said the family's decision "is great. It shows the family is very much behind the fight against drunk driving."

The settlement, accepted by Fairfax County Circuit Court Judge Barnard F. Jennings on Monday, includes an additional provision that attorneys for both sides agreed not to disclose, according to Guy O. Farley, attorney for the Svecs. He said it was "partly financial."

As is standard in out-of-court settlements, Cronin admits no liability for Svec's death by agreeing to pay the $100,000, according to attorneys for boths sides.

The accident occurred May 13, 1983. Cronin, driving home from a party where she later testified she drank six beers, struck Svec as he walked along the side of Little River Turnpike with three friends. All four teen-agers were wearing military camouflage clothes and had blackened their faces with burnt cork.

Cronin, who was acquitted of involuntary manslaughter in the death, testified at her trial that she didn't see the boys until she struck Svec.

Police records showed her blood alcohol level was .14 percent at the time of the accident. In Virginia, a level of .10 percent is considered legally intoxicated.

After her aquittal on the involuntary mansluaghter charge, her trial on a driving-while-intoxicated charge was barred as violating the constitutional prohibition of double jeopardy.

Cronin's aquittal shocked and outraged drunk driving opponents, and yesterday Mrs. Svec said settlement of the civil lawsuit constituted "a form of justice, since there was no justice in this case. . . . She was guilty."

Cronin, who was recently transferred from her post at Bethesda Naval Hospital to a military post in Florida as part of routine rotation of personnel, could not be reached for comment.

Her attorney, Robert L. Ellis, said she is "very remorseful that the accident happened, that somebody's life was taken as a result of her operating an automobile. But she is also very much aware that it was not entirely a one-way situation as far as how the accident happened."

Farley, the Svecs' attorney, said the family agreed to settle out of court, because the $100,000 "was all there was. . . very close to the maximum we could get anyway." He said Cronin's insurance liability ended at $100,000 and said she had no significant assets of her own.

Farley said the family's desire to put the incident behind them was also a factor in agreeing to the settlement. The Svecs have three other children.

Ellis, Cronin's attorney, said the settlement constituted "a compromise."He cited sympathy for the family and a general atmosphere that is anti-drunk driving as elements in favor of Svec's family, and noted the manner in which the boys were dressed and the place they were walking as elements in Cronin's favor.