L. Linton Deck Jr., the head of the Orange County, Fla., school system, was named Fairfax County school superintendent yesterday after a four-month search during which more than 100 candidates were considered for the job.

Deck, 50, was widely praised for management abilities he is expected to bring to the Fairfax system -- with 128,000 students, the Washington area's largest and 10th largest in the nation.

School Board Chairman Rodney Page said those abilities helped distinguish Deck from the other candidates to succeed superintendent S. John Davis, who left to become Virginia superintendent of public instruction last May.

Deck is expected to take over the $59,000-a-year job in mid-January. His contract will run until June 1981.

At a press conference yesterday, Deck answered most questions about specific issues in Fairfax by saying he will study them over the next several months and talk at length when he feels knowledgeable.

The Fairfax schools have a teacher morale problem caused in part by the county government's refusal to give teachers the raises to which they claim they are entitled. A "work-to-the-rule" job action in which some teachers have refused to perform extracurricular activities began last spring and is still in effect.

Asked about teacher morale and their continuing protest, Deck replied; "To some degree, that problem seems to be universal. I need to learn more about the situation to make some kind of assessment."

Gerry Gripper, president of the Fairfax County Education Association, which organized the teacher protest, said following the press conference: "It suddenly struck me as I was sitting there that he [Deck] may not be fully aware of the extent of the stiuation.I hope he has been told just how low teacher morale really is."

Joan King, president of the Orange County Classroom Teachers Association, said she has mixed feelings about Deck. "The areas he needs to work on are his commitment to parent involvement and the need to establish better relationships with teachers," King said, adding, "I'm sure he'll go into his new job with a good attitude and they [teachers] will be able to build on that."

Deck was highly praised by other Florida associates, and has been acclaimed by educators there for everything from being "an outstanding administrator" to having a "beautiful voice."

Ethel Kennedy Lyon, a member of the Orange County School Board, said, "You can look forward to great things in Fairfax County. [Deck] is one fine administrator and a very academic man."

Deck, educated at Davidson College in Davidson, N.C., George Peabody College in Nashville and Harvard has served in several school systems. He was assistant superintendent for instruction in Alexandria in 1966-67, and is a former superintendent of the Bibb County schools in Macon, Ga., and assistasnt superintendent of the Nashville metropolitan schools.

He went to Orange County, which includes Orlando, in 1973 with a mandate to remove politics from school staff appointments, according to school administrators there. The administrators said he accomplished that in little more than a year.

They said Deck's six years with the 80,000-student system were marked by only one controversy, which involved a school closing.

Last year, at a time when Deck says many citizens of Orange County were worried about the possibility of school closings, he circumvented the state's so-called sunshine law, which forbids closed meetings by two or more school board members. Deck met privately with one board member to discuss the status of a junior high school.

After that school was closed, parents of its students filed suit. A Florida appeals court found the Orange County School Board in violation of the law; the case is on appeal to the state supreme court.

Asked if that controversy were taken into consideration by the Fairfax board, Page said it was but it wasn't a decisive factor.

"Linton Deck was very forthright about the matter," Page said. "We came to two conclusions after we talked about the sunshine law issue: one, that we were glad we weren't in Florida, and the other is that Deck is very candid."