Joseph Fagan, an attorney with a national association of nonunion building firms, has been chosen by Prince George's County Executive Lawrence J. Hogan to manage the county's labor negotiations, administration sources said last night.

Incoming Coutny Attorney Robert Ostrom said that Hogan decided to hire Fagan "over two weeks ago. He thought he would be the best man for the situation and also very good for the county," Ostrom said.

Ostrom added that he had met with both Hogan and Fagan to discuss Fagan's role in the administration. The county has 11 labor contracts expiring June 30.

Hogan took an extremely conciliatory tone toward the county's labor unions during his campaign against Winfield M. Kelly Jr., and his decision to hire Fagan came as a surprise to many county labor leaders because of Fagan's background as an attorney for the Associated Builders and Contractors in Washington.

Hogan was executive vice president of ABC until March 13 when he was fired after a series of disputes with ABC director Joseph A. Burton over personnel appointments.

Fagan will be in the personnel office but also will work closely with Hogan and Ostrom as well as the as yet unamed personnel director. He is expected to leave ABC on Jan 12, sources said.

Hogan said repeatly this fall that he favored binding arbitration if collective bargaining contracts reached an impasse. Largely because of that stance he received strong support from one of the county's strongest labor unions, the Fratenal Order of Police.

Last night, FOP president Laney Hester, expressed surprise at Hogan's decision. "I just hope that ABC was just a job to Fagan and not something he believed in," Hester said. "I hope he realizes he's in a different job now. But if Hogan sticks to his binding arbitration promise I don't care who we bargain with."

"I feel at a loss because I don't know much about him (Fagan)," said Paul Manner, who will be representing five county unions of government employes at the bargaining table.

"But I really care nore about the man that where he came from."

In addition to his work for ABC, Fagan has a long record of labor work. He was director of the Wisconsin State Department of Industry, Labor and Human Realtions between 1965 and 1969 , and was executive director of the U.S. Equal Employment Opportunities Commission during 1970-1971.

Before joining ABC, Fagan also was director of the Mechanical Contractors Association of Connecticut.

Neither Hogan or Fagan could be reached for comment last night.

Robert T. Ennis, Hogan's chief aide, said last night that he would have no comment on the report of Fagan's appointment.

County Council members who were reached yesterday said they were not aware of Fagan's hiring. If Hogan decides to appoint Fagan to a county merit system position, rather than making hime a department head, his hiring will not be suject to the coucil's approval.