Members of a presidential study commission on antitrust yesterday adopted a change in the antitrust laws to make it less difficult to prove that companies are attempting to monopolize markets.

The recommendation was contained in a report adopted yesterday by the 22-member National Commission for the Review of Antitrust Laws and Procedures. The report will be sent to President Carter and Congress in January after a final meeting scheduled for Jan. 16.

The report approved yesterday complains that most courts have adopted "an unnecessarily strict standard" for providing the "dangerous probility of success" necessary to establish an attempt to monopolize under the Sherman Act.

The prevailing standards, in effect, require proof that the company holds a near-monopoly market share, a requirement that may prolong a court proceeding unnecessarily, the commission said.

The commission said it would recommend that the law be changed to allow a court ruling upon proof of unambiguously anticompetitive conduct without the lengthy market analysis that is now standard.

"Conduct that cannot serve any competitive purpose and is inherently destructive of competition" can be held to violate the law without precise definition of the market affected or extensive consideration of the company's market position, the commission said.

Extensive and complex proof relating to the market definition is necessary only if the outcome of the inquiry is likely to affect the court's assessment of the conduct's competitive impact, the report said.

The report also suggests a congressional inquiry aimed at strengthening the ability of the antitrust laws to deal with "persistent monopoly power." The commission said current legal process under the antitrust laws does not remedy persistent monopoly power effectively, in part because too much time is taken in trials to try to prove deliberate conduct designed to create or maintain monopoly power. The report said that conduct can be presumed where persistent monopoly power is shown.

The commission also recommended that structural reform-such as divestiture-rather than conduct or injunctive reflief. Should be the presumed remedy whenever a violation of the merger or antimonopoly laws has been found.

The commission admonished the courts that, when structural relief is ordered, it must be sufficient to bring about workable competition in the market even if the relief necessary has adverse tax or other financial consequences for the divesting firm or third parties.

The commission also urged that preliminary relief should be made easier to obtain whenever serious, substantial and difficult antitrust issues have been raised, and where the balance of equities favors the plaintiff.

Commission members wound up almost six months of work yesterday at a lengthy meeting that resulted in many changes to a 380-page draft report prepared by the staff. The changes, however, did not alter the report's basic pro-competition thrust.

In other chapters, the commission adopted recommendations designed to expedite complex antitrust cases. One recommendation was that judges seek to manage and control the cases in a better fashion, use time limits and control discovery.

The commission also urged Congress to re-examine-and revoke some-antitrust immunities in the agricultural, insurance, surface transportation and ocean shipping industries.

The commission only can make recommendations, but its members include key members of the judiciary and antitrust committees of Congress, including Sen. Edward M. Kennedy (D-Mass), who becomes chairman of the Judiciary Committe in the new Congress, and Rep. Peter Rodino (D-N.Y.), chairman of the House Judiciary Committee and its monopoly sub-committee.

The commission's chairman is John H. Shenefield, assistant attorney general in charge of the Antitrust Division. Also on the panel is Michael Pertschuk, chairman of the Federal Trade Commission, which shares antitrust enforcement powers with Justice.