The U.S. Court of Appeals here yesterday reinstated the 1981 Abscam conviction of former representative Richard Kelly (R-Fla.), saying that, contrary to the ruling of a lower court judge, the government had not engaged in outrageous conduct in offering Kelly a bribe.

Kelly, who maintained that he was trying to conduct his own investigation of the people who bribed him, was convicted in Washington after federal jurors saw a videotape of him stuffing $100 bills into his pocket. He was defeated in the 1980 primary.

Last May, senior U.S. District Court Judge William B. Bryant threw out the conviction, saying that the FBI had violated standards of due process by, in effect, creating a crime and a criminal.

Disagreeing, Chief Appeals Judge Spottswood W. Robinson III and Judges George E. MacKinnon and Ruth Bader Ginsburg yesterday ruled that the FBI's Abscam operation did not reach the level of outrageousness "which would bar prosecution of the corrupt officials that were uncovered, particularly given the difficulties inherent in their detection."

"We are pleased the Court of Appeals agrees with our position," Justice Department spokesman John K. Wilson said yesterday.

The six congressmen and the senator charged in the Abscam cases have now been convicted.

All but Kelly and former representative John W. Jenrette Jr. (D-S.C.) have been sentenced to prison. U.S. District Court Judge John Garrett Penn has been criticized privately by prosecutors for failing to sentence Jenrette, who was convicted 2 1/2 years ago. Twice in the past year, Penn has permitted Jenrette to leave the country--once to go to England and more recently to Mexico, according to court records. No explanation has been offered for the delay.

Abscam for Arab scam began in 1978 with an FBI undercover operation to recover stolen art and securities.

Kelly was convicted of taking $25,000 of a promised $250,000 from FBI undercover agents in return for agreeing to introduce a bill to help solve immigration problems for an undercover agent posing as an Arab businessman. Kelly admitted taking the money, but said that he did it as part of his own investigation of some "shady characters."

The appeals court ruled that before the FBI offered Kelly the bribe the Abscam operatives had "evidence from which they could conclude that Kelly was, in fact, corrupt."

The court found nothing wrong with employing a convicted confidence man to offer the bribe.