The board of regents of the University of Maryland barred future investments of university funds from businesses operating in South Africa yesterday unless the firms have agreed to follow guidelines designed to raise the economic, educational and social opportunities for that nation's blacks.

The restriction, approved in a meeting at College Park, goes into effect July 1 and affects new investments for two years. University President John Toll said the policy revision reflects a bill passed by the General Assembly this year that also restricts investments of new state pension funds to companies that have signed the guidelines, called the Sullivan Principles.

"I think it is a responsible action. Since we are a state institution, we should be in harmony with state policy," Toll said.

The university had invested almost $7.1 million -- 23 percent of the $30 million in total university investments -- in 16 companies that do business with South Africa as of March 31. Each of the 16 firms has signed the guidelines, according to Anne Moultrie, university director of media relations, but the university withdrew $7,000 from Dun and Bradstreet in April because it had not signed the Sullivan Principles.

The new policy also will require companies receiving university investments to show proof annually that they have made sufficient progress in improving the life of blacks they employ in South Africa.

The new policy "will be a constraint on our investment fund managers, but we believe that most responsible American companies can adopt the Sullivan Principles," said Toll, who initiated the policy. "It will still permit us to have an effective investment program."

The regents' finance committee had approved the policy revision in May.

The board also established 10 regent scholarships for students of "extraordinary merit." The awards will be worth $6,000 a year to undergraduates and $10,000 a year for graduate students.

The board also adopted new room and board fees for the 1985-86 school year. The typical annual dormitory charge per student for a double room was increased at all campuses except College Park, which at $1,842 has the highest charge. The average charge for full board will range from $1,190 at the Eastern Shore campus to $1,578 at the College Park campus, reflecting an average increase of $68, or 6 percent, over the 1984-85 rates.

The board's finance committee approved a proposal to raise student activity fees at College Park from $18 to $28 for full-time students and $10 to $16 for part-time students. The full board will vote at its August meeting.