President Reagan yesterday nominated Douglas H. Ginsburg, an administration proponent of industry deregulation, to serve as assistant attorney general for the Justice Department's antitrust division.

Ginsburg is expected to continue the administration's antitrust policies, which have stressed the importance of considering foreign competition and economic efficiency in evaluating proposed mergers of large corporations.

Senate Republican sources said Ginsburg is expected to win confirmation without problem.

Ginsburg, 39, would succeed J. Paul McGrath, who resigned April 1 to return to a New York law firm. He would replace Charles F. Rule, who has served since April 1 as acting assistant attorney general for the antitrust division.

Ginsburg, currently an official in the Office of Management and Budget, worked in the Justice Department's antitrust division from 1983 to 1984 as a deputy assistant attorney general for regulatory affairs under McGrath's predecessor, William F. Baxter.

Baxter, now a professor at Stanford University School of Law, said Ginsburg was a "terrific" choice. "Doug is very, very smart. . . . He knows the antitrust area very well and knows the regulated industries area even better."

Ginsburg is likely to continue in the "economically oriented" tradition of Baxter and McGrath and "will not pursue the mindless populism of the late 1960s and early 1970s," Baxter said. The "economically oriented" approach focuses on whether a proposed merger might violate antitrust laws by restricting competition in a way that would reduce output and raise prices, he said.

Antitrust theory of the 1960s and early 1970s took a different view of mergers by firms in the same industry and considered "social" factors such as the impact of a merger on local communities or the desirability of maintaining a number of competitors in each industry.

Baxter, who was known during his tenure for his outspoken manner, described Ginsburg as "soft-spoken, and probably more politically tactful and skillful than I am."

Before joining the government, Ginsburg was a Harvard Law School professor from 1981 to 1983 and an assistant professor from 1975 to 1981, specializing in antitrust and economic regulation.

As OMB's administrator for information and regulatory affairs, Ginsburg was responsible for implementing an executive order directing federal agencies to ensure that regulations are "as cost-effective as possible and otherwise consistent with administration policies," the Justice Department said.

Ginsburg also directed an administration program to compile information on all "significant regulatory activities currently under way," which will be published soon, the department said.

A graduate of Cornell University and University of Chicago Law School, Ginsburg served as a clerk for the U.S. Circuit Court of Appeals and for Supreme Court Justice Thurgood Marshall.