Alexander Gudunov, the Soviet dancer who defected from the Bolshoi Ballet last month in New York, has joined the American Ballet Theater, and will make his company debut as a principal dancer at the Kennedy Center in Decmeber.

Gudunov, 29, whose dancing has been compared to ballet superstar Mikhail Baryshnikov's, another Soviet defector, has signed a one-season contract for the 1979-1980 season with the company, an ABT spokesman said yesterday.

"We're very pleased that Godunov will be with us this year," ABT director Lucia Chase said. "He is a great artist with superb Russian training."

Godunov, who is expected to join rehearsals when they start in New York on Oct. 29, said he was "thrilled" to join the company.

"For six years, ever since my first visit to this country," said Godunov in a translated statement supplied by an ABT spokesman, "I have dreamed of expanding my artistic horizons and participating in the choreographic innovations of the West."

Baryshnikov, who is dancing with the New York City Ballet during their current performances at the Kennedy Center yesterday, called Godunov "a wonderful dancer." Baryshnikov, slated to join ABT as artistic director next year, said, "I don't see why not" when asked if he would be happy to work with Godunov.

Most ballet observers had expected the classically trained Godunov to join the ABT, since its repertoire is mainly classical. Godunov has danced all the lead male roles in the Bolshoi, including Albrecht in "Giselle," Basil in "Don Quixote" and Vronsky in "Anna Karenina."

"Giselle" is the scheduled opening production of the ABT'S Kennedy Center run -- from Dec. 4 through 30 -- also the beginning of the ABT season.

According to the company's general manager, Joyce Moffatt, "It is yet to be decided what Godunov will dance in."

Godunov first gained nationwide attention last month during his performance with the touring Bolshoi company. Following his defection, his wife, Ludmilla Vlasova, a dancer in the Bolshoi troupe, abruptly returned home before the end of the tour. American officials detained her plane at Kennedy Airport for three tense days in an effort to ascertain whether she was leaving of her own accord.

Godunov was the first in a series of five Russian artists -- two other Bolshoi dancers and two champion iceskaters -- who have defected during the last month, reportedly causing the Soviets great embarrassment and probably triggering the cancellation last week of the Moscow Symphony's scheduled appearance here.

Roger Stevens, chairman of the board of the Kennedy Center and a member of the ABT board, said yesterday that he had no idea that Godunov had signed with ABT. "They didn't discuss it at last Friday's (ABT) board meeting" in New York, Stevens said.

Asked if he would extend ABT'S four week run at the Kennedy Center, Stevens said no. "It's written in iron," he said. "But they come back again for a few weeks in the spring."

"I think he'll be very good," said Stevens about Godunov. "He'll give the company a little more glamor -- for lack of a better word."