The Supreme Court yesterday gave Congress an important victory over the president in a constitutional power struggle that has been waged for nearly a half-century.

The justices let stand a decision upholding the one-house veto, which enables either the House or the Senate to decide unilaterally whether any of a wide range of governmental actions will survive.

Congress has passed numerous laws undeer which an executive agency can take certain actions, such as issuing regulations for federal elecitons, but where either the House or the Senate can cancel the actions with a one-house veto.

About 300 provisions of 200 law incorporate this one-house veto, allowing for potential congressional disapproval of programs under which 13 Cabinet departments and other governmental units spend billions of dollars annually.

Every President since Herbert Hoover, supported by the Justice Department, has argued that the one-house veto is an unconstitutional incursion into the executive domain, although various administrations have endorsed the device for specific, limited uses.

In November, for example, President Carter vetoed the Deparment of Energy Authorization Act of 1978 because "it limits the constitutional authority of the President through three one-house veto provisions." Earlier, however, he had approved the one-house veto in the Executive Reorganization Act, terming his approval a "narrow exception."

The decision left standing yesterday was handed down in May by the U.S. Court of Claims, which voted 4 to 3 to uphold the one-house veto.

The judges agreed with lawyers for the House and the Senate that the device was permitted by the "necessary and proper" clause in which the Constitution gave Congress wide discretion to decide how to do its job.

The court rejected the position of the Justice Department, which, presumably in behalf of Congress as well as the executive branch, "conceded" that the one-house veto violated the constitutional separation of powers.

The court acted in a case brought by 140 federal judges who complained that in a 6 1/2-year period ended Oct. 1, 1975, the government had held their salaries constant while inflation eroded their real compensation by 34.4 per cent. The net result, they contended, was a violation of a provision of the Constitution barring reductions in judges' pay.

The judges based one of their main arguments on the Federal Salary Act of 1967, which contained a one-house veto provision until last April, when Congress eliminated it.

In March, 1974, President Nixon recommended a judicial pay increase in each of the fiscal years 1974 through 1976, for a total of 24.23 per cent over existing salary levels: $40,000 for district judges, $42,500 for appellate judges.

But the Senate exercised the one-house veto to block the recommendation. This was unconstitutional, the judges claimed. The Court of Claims majority - whose own salaries were at stake - ruled otherwise.

In briefs in the Supreme Court, the Justice Department said that "a clear resolution of the constitutional issues" was both urgent and of "the utmost importance" because the one-house vetoes in numerous laws "have substantially encroached upon the constitutional functions of the President and in many cases of the judiciary as well . . ."

The department also said that the Court of Claims decision is the only one to date "that squarely reaches the issue." But, the department said, the Supreme Court should not review the Claims Court decision because the repeal of the one-house veto provision in the salary law would make an ultimate ruling "largely advisory."

At the same time, the department contended that the provision Congress repealed was one that could not be severed from the pay law. The Court of Claims termed that contention "patently ludicrous."

The judges' counsel in the case, Stephen G. Breyer, told the court in a reply brief that if the department was correct in saying that the pay law's one-house veto was both unconstitutional and not severable, then every salary payment since 1969 made to federal employees as well as judges was illegal. Yet the deparment had not tried to block salary payments, he told a reporter.

In other actions, the Supreme Court:

Declined to review a decision allowing the Nassau County. N.Y., Medical Center to fire medical technologist Margaret Townsend, a black who for eight years had done her job with unquestioned competence, on the ground that she lacked the bachelor of science degree the county decided was needed.

Let stand a ruling that the Chicago suburb of Maywood could order current employees who live elswhere to move into the village.

Gave environmentals a victory by letting stand a ruling that the Commerce Department had violated a law intended to assure that baby seals from South Africa are not prematurely harvested for fur coats.

Agreed to review a ruling that a Dallas plan for at-large election of three of eleven councilmen unconstitutionally discriminated against participation by Hispanics in the electoral process of the Texas city.