Mayor Marion Barry, who marked the start of his first term six years ago with a trip to Africa, plans to return there in early December to attend an international conference of black mayors and to tour four countries.

Barry has spent a good part of this year out of town, campaigning for presidential candidate Jesse L. Jackson and leading a District delegation of officials and businessmen on a 13-day goodwill and trade mission to the Far East.

As president of the National Conference of Black Mayors, Barry will depart the weekend of Dec. 7 with about 22 other black mayors for Monrovia, the capital of Liberia, to take part in the first meeting of the newly formed World Conference of Black Mayors, according to aides.

Barry is a board member of the fledgling World Conference, which was founded last April in St. Louis and is headed by Mayor Johnny Ford of Tuskeegee, Ala. Barry and the mayors also will visit Dakar, Senegal, which is one of the District's international sister cities.

"The mayor hopes to meet with the mayor of Dakar and cement that relationship," Pauline Schneider, Barry's director of intergovernmental relations, said yesterday.

Then Barry will break away from the group to travel to the Sudan, at the invitation of that country's president, and on to Somalia, before returning to Washington just before Christmas.

City funds will be used to pay the mayor's travel, hotel and food costs that are not picked up by the host countries, according to Schneider.

The mayor will be accompanied on the trip by Ann Simpson Mason, a member of Schneider's staff, and possibly Courtland V. Cox, a longtime aide to the mayor who specializes in international trade and who accompanied Barry on his first trip to Africa.

Cox said yesterday that the international conference in Monrovia will devote considerable time to discussing ways to increase trade. Cox said he has been invited to address the group, although the "details are still to be fleshed out."

Barry could not be reached for comment yesterday. Annette Samuels, the mayor's press secretary, said, "My understanding is that it's a trip with regard to developing relations between black [U.S.] mayors and African mayors."

A little more than six months after taking office in 1979, Barry left on a 20-day trip to Senegal, Liberia, Kenya, Zambia and Tanzania. He was accompanied by his wife, Effi, bank executive Carter H. Dove, attorney Robert B. Washington Jr. and Cox, who at the time was the city's minority business opportunities chief.

An exhausted mayor returned from that trip saying that the example of the Africans he met showed him that his city government "ought to get way more" in services for the tax dollars were being spent.

He also said he returned "more profoundly convinced that we have to be more actively involved in the struggles of our [African] brothers and sisters."

Barry took his only other major overseas trip as mayor last May, visiting the Far East. He signed an agreement with the mayor of Peking, to hold import-export trade shows there and here next year.

Sixteen companies, including at least five that have done business with the D.C. government, together donated $20,000 to help pay for sending Barry, his wife, City Council Chairman David A. Clarke and five other city officials on that trip.

The remainder of the cost for air travel and reciprocal ceremonies and receptions was paid for by the tax-financed Mayor's Committee to Promote Washington D.C. and $4,500 in additional city funds.