Acting Maryland Gov. Blair Lee III survivied his first test of strength today when the House of Delegates upheld the veto of a bill that would have committed the state to an annual 5 per cent increase in welfare payments until 1982.

The welfare measure was vetoed last spring by Gov. Marvin Mandel, but Lee asked his lobbyists to strenuously fight against an override because he said the bill committed the state to spending it cannot afford.

The House decision to uphold the veto was widely interpreted as a victory for the acting governor. "It shows Lee has mor muscle than some people thought he had," said Del. Paul E. Weisnegoff (D-Baltimore), who voted against Lee on the veto issue.

Last week, the Senate overrode the veto, setting the stage for a final showdown in the House. The measure called for yearly increases in benefits for state welfare recipients. If approved, it would have raised monthly benefits from $254 now to $314 by 1982.

Lee has proposed a 5 per cent increase in benefits for next years, but opposed the four year commitement. Once he said he would seek to protect the veto, the contest became billed as a test of the acting governor's ability to shape legislative events.

The issue inspired emotional debate in the House with opponents of the override calling for fiscal restraint and supporters asking for legislative commitment to the 207,000 welfare receipients in Maryland who would have benefited from the guaranteed increases.

There were several references to the active lobbying of administration aides in recent days. Del. Lena K. Lee (D-Baltimore), who supported the override move, said many minds were made up as result of "armtwisting and tricks" of the acting governor's lobbyists.

"I would rather deal with my peers than deal with a superior who has the power to veto my bill, a superior who has the power to give me a bridge or a road in exchange for something (a vote) that's going to make people hungry," she said from the House floor.

The final vote of 76 to 59, which fell nine votes short of the three-fifths majority needed to override a veto, divided the House membership along geographic, party and ideological lines.

The Democratic chief executive found himself supported by Republican members as well as delegates from rural Eastern Shore and Western Maryland districts and conservative pockets int he Baltimore suburbs.

Delegates from black, urban districts in Baltimore and Prince George's County lined up with most members of the largely liberal Montgomery County delegation in support of the override move.