WASHINGTON, May 17— Arnaud de Borchgrave, editor in chief of The Washington Times for the past six years, is relinquishing editorial control of the newspaper and will be suceeded by Wesley Pruden, the managing editor.

Mr. de Borchgrave, who made his reputation as a flamboyant foreign correspondent for Newsweek, joined The Times in 1985. Now 64 years old, he will continue to work for the newspaper as editor at large, he said, pursuing stories in Washington and abroad. "I have believed in scoops all my life, and I intend to pursue them even it seems a little old-fashioned today," Mr. de Borchgrave said.

Mr. Borchgrave, who announced his decision on Thursday, said the move signals no change in editorial direction of the newspaper, which is published five days a week and plans to add Saturday and Sunday editions in September.

The Washington Times is owned by New World Communications, a subsidiary of business interests affiliated with the Unification Church, which is based in South Korea. The church was founded by the Rev. Sun Myung Moon.

The newspaper, which has a conservative editorial policy, has been struggling to find a place in a Washington market long dominated by The Washington Post.

Since its founding in 1982, The Times has lost more than $250 million, Times officials say. Its circulation is about 100,000 papers a day, said Steve Ranzer, director of advertising.

Readers buy The Washington Times to find out what conservatives are thinking and doing. Its critics contend that it colors the news to conform to the right-wing views of its backers. In 1987, the head of the editorial page, William P. Cheshire, and four editoral writers quit, contending the publication had lost its editoral independence.

Mr. de Borchgrave dismisses such complaints, insisting that while the paper's opinion pages are conservative, the news is presented objectively.

Mr. Pruden, who joined The Times as chief political correspondent three months after it was founded, became assistant managing editor the next year and managing editor in 1985. He will retain his title of managing editor and will continue to write a column that appears three days a week.

He was out of town and could not be reached for comment, but in his column today he wrote, "Arnaud had never worked on a newspaper before he came to The Times but he hadn't been here long before the newsroom felt like something out of Ben Hecht's 'Front Page,' or at least Evelyn Waugh's 'Scoop.' "