Securities and Exchange Commission Chairman Harold M. Williams said yesterday he expects President-elect Ronald Reagan to name a new chairman of the regulatory commission but said he is prepared to stay.

"If I had to bet, I would bet that the president will pick his own chairman. It's been ever thus," said Williams, who has made no secret of his desire to remain at the helm of the commission.

Williams said he has not been contacted by Reagan or his aides. Although he has met with the transition team at the SEC, Williams said he believes the transition team is not involved in the issue of the chairmanship.

Among those said to be under consideration as successors to Williams are Alan Levenson, a securities lawyer with the District firm of Fulbright & Jaworski; David Ruder, dean of the Northwestern University law school in Evanston, Ill.; and Bruce Mann, a securities attorney in San Francisco.

Williams, who has been criticized for imposing a lack of momentum on the SEC, yesterday surveyed his tenure at the commission with some apparent satisfaction and a few mild regrets about initiatives that he may not be around to carry out.

Among his accomplishments, Williams counted "the progress and the nature of the progress made toward a national market" to link the nation's major stock market systems. Rep. Bob Eckhardt (D-Tex.), in a recently published report, criticized that pace as too slow, but Williams said yesterday, "I don't think we are entitled to take a lot of risk in the process of improving (the present market system)."

Williams also said he was pleased with the agency's emphasis on capitall formation as a responsibility along with the SEC's responsibility to investors.

Inflation accounting, a process in which major corporations are required to restate their financial results taking into account the effect of inflation, "may over time be the most important development in a long time in the area of disclosure," he said, indicating another area of accomplishment.

Williams said that the commission would not defer any issues or speed up consideration of any because of the impending transition.

His chief regret about leaving, if he is asked to step down as chairman, would be "that there are still some issues in the shaping process that I would like to have been part of," he said. Williams said he would not finish his five-year term as a commissioner if he were asked to step down from the chairmanship.