Paul Masem, superintendent of the Ames, Iowa, school system who was active in desegregation efforts in Arkansas, has been chosen as Alexandria's school superintendent, School Board officials announced yesterday.

Board Chairman Timothy S. Elliott called Masem "experienced, intelligent . . . a sensitive human being" and "a man of vision." He said Masem was the board's unanimous choice.

Masem, 48, will succeed Robert W. Peebles, Alexandria's superintendent since 1980, who cited health reasons for retiring from the $77,742-a-year post as head of the 9,600-student system. Masem, who takes over on Aug. 17, will be paid $83,000 a year.

Masem is credited with pulling the 5,000-student Ames school district out of financial trouble, promoting a tax increase to supplement the school's budget and expanding the role of parents and others in such tasks as school closings and reorganizing secondary schools, according to school officials and Iowa newspaper accounts.

Alexandria school and city officials cited Masem's desegregation efforts in Little Rock, Ark., where he was superintendent from 1978 to 1982, as giving him an advantage over the two other finalists.

In Arkansas, Masem helped initiate an expanded, court-ordered desegregration plan that involved consolidating two mostly white suburban school districts with Little Rock's district, which had a 71 percent black enrollment.

Masem said yesterday that his desegregation efforts in Little Rock came at a time when the school board there was increasingly opposed to desegregation attempts and, at one point, asked the court to lift its mandate. By mutual agreement, the school board and Masem decided to end his contract a year before it was to have expired.

Masem said that narrowing the academic performance gap between minority and white students, which has been a priority of the Alexandria School Board, will be one of his goals. The city's enrollment is 40 percent black and 20 percent other minorities.

During his recent interview with Alexandria community members, Masem emphasized his skills in curriculum development, which he said have won national recognition. His strategy, he said, is to actively involve teachers in the process.

The process the School Board used to choose a superintendent was criticized by some Alexandria City Council members who thought their views should have been given greater consideration. However, Masem was reportedly the choice of several council members.

Council member Redella S. (Del) Pepper (D) said yesterday that she was delighted with the board's decision. "Because of his experience in Little Rock, all of us felt Paul was head and shoulders above the rest," Pepper said. "He just had all the right answers . . . . He has a lot of savvy."

Masem has also worked in administrative positions in several Maryland districts, including Montgomery County, where he was an associate superintendent from 1977 to 1978, Hagerstown and Washington County.

He grew up in New York City and has a doctorate in school administration from Vanderbilt University in Nashville. He is married and has three children.

Of his new job, he said yesterday: "It just sounded like someone wrote the job description for me."

Masem is the second former Little Rock school superintendent to be named to head a Northern Virginia school system recently. In May, Edward Kelly, who had been Little Rock superintendent since 1982, was appointed Prince William County superintendent.