Martin C. Anderson, a prominent member of the Reagan inner circle and one of the administration's most outspoken conservatives, will quit as director of the White House Office of Policy Development and return to private life, he said yesterday.

Anderson, 45, whose resignation is scheduled to be announced today, was praised by White House counselor Edwin Meese III as "the conscience of the administration."

His departure is certain to spark new concerns among conservatives who believe that ideologically loyal supporters of the administration are being eliminated systematically by a pragmatic faction headed by White House chief of staff James A. Baker III.

But high-level administration sources said last night that Anderson is leaving at his own initiative and largely for personal reasons, not because of any policy dispute. One high official said it was simply that "Marty wants out."

Anderson, who frequently held up Reagan's campaign promises as a test of policy in discussions within the administration, late in November was offered the vice chairmanship of the Federal Reserve Board. The presumption was that this would lead to the chairmanship when Paul A. Volcker's term as chairman expires next year. Anderson declined, and instead told Meese that he planned to leave the administration.

The supporters of Anderson, especially Meese, praised him for effective policy formulation. But his critics said that Anderson was miscast as director of a 41-member policy staff because he was, in the words of one of them, "a thinker, not a manager."

Anderson, an economist and author who was Reagan's chief issues adviser during two presidential campaigns, did not see his role as that of an innovator of a host of new policy proposals. He said yesterday that he considered the Office of Policy Development to be "an implementer" of basic Reagan economic policies and that it had accomplished this purpose.

Anderson said he will return to his post as senior fellow of the Hoover Institution at Stanford University, one of the bastions of intellectual support for the administration.

However, he will spend much of his time in Washington writing a book about the political movements that led to the Reagan presidency, he said. His wife, Annelise Anderson, also an economist and author, will remain as a deputy to budget director David A. Stockman.

Anderson is known as a conservative with a strong libertarian streak. He tended to oppose government intervention on any issue, which sometimes brought him into conflict with the New Right.

He was an architect of the proposal in the Nixon administration for the all-volunteer Army. Within the Reagan administration he was one of the few White House insiders to oppose the proposal for new excise taxes, which the president rejected after a long internal struggle.

But Anderson also was on the losing side on several issues, such as the limits on Japanese auto imports, which Reagan accepted under the euphemism of "voluntary restraints."

And he came under consistent fire from the pragmatists, which some conservatives describe as the "Baker-Bush" faction within the White House. One of these described conservatives as becoming "an extinct breed" within the administration, and pointed to the previous departure of long-time Reagan loyalists Lyn Nofziger and Richard V. Allen.

On the surface, at least, Anderson's departure is also a blow to Meese, who was blemished by the clouded departure of Allen and the subsequent appointment of William P. Clark as national security affairs adviser with independent access to the president.

But the real effect on Meese will be determined by the choice of Anderson's replacement. White House officials said no decision had been made. One possibility for a replacement is considered to be Edwin L. Harper, a deputy director of the Office of Management and Budget with experience in domestic affairs. Another name that was mentioned was Transportation Secretary Drew Lewis, but this was denied by White House officials.

Though Anderson is leaving the administration, he is not severing his ties with it. The president, who asked him to stay in a meeting earlier this week, will appoint his long-time supporter to the Economic Policy Advisory Board and the Foreign Intelligence Advisory Board, an unusual dual responsibility.

Anderson said he also expects to serve as a consultant to the administration on particular issues.