President Reagan's cabinet advisers have recommended that he seek a fundamental revision of federal antitrust laws governing corporate mergers and price-fixing penalties, to bring these statutes in line with "economic realities," sources said yesterday.

A key proposal would ask Congress to change the 71-year-old Clayton Act, one of the two pillars of antitrust enforcement, to lessen uncertainty over the legality of mergers. The language in Section 7 of the Clayton Act prohibiting mergers that "may" lessen competition or "tend to create a monopoly" is so vague that it inhibits some mergers that would improve competition and strengthen markets and industries, administration officials say. The goal would be to remove this barrier, sources said.

The proposed changes were agreed to Wednesday at a joint meeting of the cabinet councils on domestic policy, headed by Attorney General Edwin Meese III, and economic policy, led by Treasury Secretary James A. Baker III. Another meeting is necessary to approve final language of the proposed Clayton Act revisions, sources said.

If approved by the president, the proposals would be sent to Congress early next year, Justice Department officials have said. Despite strong support from business, the reform proposals are likely to face an uphill struggle, particularly in the House.

Congress would also be asked to write into law the revisions in merger guidelines and antitrust enforcement policies adopted during the Reagan administration, sources said.

These revisions constitute "a quiet revolution that is remaking the map of American industry," in the words of Deputy Assistant Attorney General Charles F. Rule. In a speech this month, Rule said the administration's goal was to "deregulate" antitrust, not eliminate it, by encouraging beneficial mergers and joint research projects by businesses and giving entrepreneurs more opportunity to profit from inventions and "intellectual" property.

The cabinet advisers acted Wednesday on recommendations from an administration working group on antitrust reform, headed by Assistant Attorney General Douglas H. Ginsburg, head of the antitrust division, and Manuel H. Johnson, Assistant Treasury Secretary for Economic Policy.

According to a report this week in Legal Times, the working group supported legislative changes to limit the treble-damage penalties that enable companies and other private litigants to collect big damage awards from other companies that lose antitrust suits.

Treble-damage penalties should be awarded only in price-fixing cases, the working group proposed, according to the Legal Times account. In other cases, violators should be liable only for actual damages, legal costs and any applicable interest payments.

The working group also proposed to provide antitrust exemptions for mergers and acquisitions in industries harmed by import competition, remove some of the current restrictions on interlocking corporate directorates, and require plaintiffs to pay the legal costs of antitrust suits if their claims are found to be "frivolous, unreasonable . . . or in bad faith," according to the Legal Times' account of the working group's recommendations.

The cabinet councils' recommendations in these areas weren't available.

Sources said the working group did not reach a conclusion on what to do with the Clayton Act, which stands alongside the Sherman Act of 1890 as the government's check on monopolization, anticompetitive mergers, price fixing and other economic collusion.

Commerce Secretary Malcolm Baldrige has campaigned for repeal of Section 7 of the Clayton Act, contending that the imprecision of that language "allows lawyers to declare you guilty before you've had a chance to let your merger plan work. The results are obvious -- opportunities for efficiency and productivity gains are stillborn because of the fear of litigation," Baldrige wrote recently.

Some antitrust attorneys in and out of government argue that Baldrige's complaints are out of date -- that federal enforcement policy and judicial rulings have confined the impact of Section 7 far more tightly than Baldridge's complaints indicate. "It's a flexible standard. It's been applied and understood," by lawyers, said Sanford Litvack, head of the antitrust division in the Carter administration.

The working group reportedly offered the cabinet committees three choices:

Ask Congress to repeal Section 7; leave it alone, or seek legislative changes in the act to reduce uncertainty and build in the revisions in antitrust policies and guidelines adopted during the Reagan administration. The councils' choice was a compromise, based on the third position, sources said.