The FBI is bringing 200 field agents to Washington to cope with the flood of requests for documents under the Freedom of Information Act.

An FBI spokesman said yesterday that, as of Feb. 11, the bureau had a backlog of more than 8,000 unanswered requests. To dispose of them, the spokesman said, Director Clarence M. Kelley is forming two special teams, each consisting of 200 agents, from FBI field offices.

The first of these teams will work on processing FOI requests at FBI headquarters until Sept. 30. It then will be replaced by the second group of 200 agents.

The spokesman described the move as "a one-shot stopgap measure" until the bureau completes establishment of a permanent staff of 375, recently authorized by Congress to process FOI requests.

Because of disclosures that the FBI engaged in covert surveillance and harassment during the 1960s and early 1970s, the bureau has received a barrage of requests from reporters and others wanting information from FBI files.

Between January, 1975, and Feb. 11 of this year, the spokesman said, these requests totaled 31,592. Of that number, he added, 23,500 have been answered, and 8,092 await processing.

He acknowledged that most of the replies have involved delays of several months because of time required to search bureau files for the requested documents and then screen them to ensure that classified information or material harmful to innocent parties is deleted.

Creation of the new 375-member processing staff will cost the bureau approximately $6 million a year, the spokesman said. He added that an additional $6.5 million will be required to pay for the two teams of agents being used on a temporary basis.