A president's power to make one-year appointments of federal judges while Congress is in recess was upheld yesterday by a federal appeals court, which rejected arguments that such appointments subject judges to political pressure.

The unilateral appointment power, first used by George Washington in 1789, "prevents the executive from being incapacitated during the recess of the Senate," said Judge Robert Beezer of Seattle in a 7-to-4 decision of the 9th U.S. Circuit Court of Appeals.

Federal judges normally must be confirmed by the Senate before taking office and then can serve for life unless impeached. A recess appointee can serve only until the end of that year's congressional session, unless confirmed to a life term.

The court said there have been about 300 judicial recess appointees in the nation's history. Yesterday's case concerned the most recent one, Walter Heen.

President Carter nominated Heen to a a U.S. District Court vacancy in Hawaii, but the Senate never acted on the nomination. In December 1980, Carter made Heen a recess appointee, and he served until the next December, when he was replaced by an appointee of President Reagan.

A woman whom Heen had found guilty of drug offenses appealed one of his rulings. A panel of the appeals court used the case to conclude in 1983 that judicial recess appointments are unconstitutional. That decision was reversed yesterday.