A University of Maryland professor pleaded guilty yesterday to accepting a bribe from a graduate assistant, as part of a scheme in which he received $12,000 intended for three graduate assistants he had hired.

Al-Tony Gilmore, 36, former director of Afro-American Studies on the College Park campus, admitted that the three assistants he hired between 1976 and last year paid him half of their stipends. Two of these students did no work as graduate assistants and one of the two, Robert G. Harris, received an A grade in each of four courses although he attended no classes, according to prosecutor Joseph L. Evans.

Circuit Judge Arthur M. Ahalt, who will sentence Gilmore in April, warned the professor that he could receive a $5,000 fine for accepting a bribe from Harris, as well as 12 years in prison, and could lose several of his citizen's rights, including the right to hold "an office of public trust," because his crimes involved corruption.

State police began investigating Gilmore at the request of university officials last summer. Police interviewed Harris, who then set up a meeting with Gilmore in a parking lot at Georgetown University.

The two men stood beside Harris' van and discussed the scheme and ways of avoiding detection, prosecutors said, while a state police detective hid under a blanket inside the van.

Gilmore, who taught at Howard University before coming to the University of Maryland in 1976, remains a tenured faculty member. He was removed from his job as department director at the request of university officials last fall, and now has a nonteaching research job in the university's division of behavioral and social sciences.

Spokeswoman Roz Hiebert said the university's office of law is waiting to obtain legal documents before deciding whether to begin the complicated procedure of revoking his tenure.

Gilmore, who refused to comment after his court appearance, agreed in court that the assistants cashed their regular biweekly stipend paychecks and gave about half the money to Gilmore. The stipends came from state funds.

Gilmore, whose annual salary is about$41,000, said he hired one graduate assistant, Sonja E. Watson, in 1976, and received almost $5,000 from her over three years. Prosecutor Evans said that "at no time was [Watson] ever required to do any work as a graduate assistant."

In 1979, after Watson completed her graduate work, Gilmore hired Harris, and said in court that he received about $5,000 from him between 1979 and last year. Gilmore said in court that he was unaware that Harris was not even enrolled as a graduate student during much of this period.

Gilmore also acknowledged hiring a third graduate student, Linda G. Holiday, and again receiving for himself about half of her stipend in cash. Gilmore required her to work only 10 of the 20 hours a week she was hired to work.

Gilmore, who was arrested last October, was originally charged with two counts of bribery, seven counts of theft and one count of obstruction of justice. Prosecutors agreed to drop all but one bribery charge, in return for Gilmore's guilty plea. Gilmore has been free on personal recognizance.