Two top Education Department officials said yesterday that the agency's new secretary, William J. Bennett, has asked them to step aside so he can fill their posts with his own appointees.

Donald J. Senese, who has served as assistant secretary for educational research and improvement since 1981, said he will resign May 1.

Manuel J. Justiz, director of the National Institute of Education, said Bennett also told him he wanted to bring "a new team on board." But Justiz said Bennett spoke only "in very general terms about the appropriate timing for the transition."

Their departures would bring to four the number of top Education Department officials who have announced their resignations since T.H. Bell stepped down as secretary last fall.

In early February, after Bennett was nominated by President Reagan but before he was confirmed by the Senate, Under Secretary Gary L. Jones announced his resignation. In a statement yesterday, Bennett said Jones will leave on March 31.

Jones, who had been vice president for administration of the American Enterprise Institute and a member of the Fairfax County Board of Education, told the Chronicle of Higher Education he "recognized that it's time to move on."

In addition, Benjamin Alexander, deputy assistant secretary for student financial assistance and a former president of the University of the District of Columbia, announced his resignation after Bell said he was leaving as secretary.

Bennett's statement yesterday, in the form of a memo to top department officials, criticized as "inaccurate and highly unfair" a report in yesterday's Washington Times that Bennett had "given walking papers" to Jones, Senese, Justiz and the department's general counsel, Maureen Corcoran.

The statement praised Jones and Senese, and said Justiz "retain s my confidence and support." Bennett also said that Corcoran "remains as general counsel" and retains his "confidence and support." Corcoran could not be reached for comment.

Senese, whose office includes both the NIE and the National Center for Education Statistics, said Bennett told him he plans to bring in "five or six people" with whom he had worked in the past to fill top Education Department posts.

"This is one of the things you get used to when you accept a political position," Senese said. "It may last two months or for four or eight years."

Both Senese and Justiz said they hope to find other positions in the Reagan administration.

According to Education Department sources, one of those being considered by Bennett, possibly for Senese's job, is Chester E. Finn Jr., a professor at Vanderbilt University and formerly a top aide on education issues to Sen. Daniel Patrick Moynihan (D-N.Y.)

Bennett formerly was chairman of the National Endowment for the Humanities, which gave substantial support to the Education Excellence Network, a school reform group that Finn helped to found.