Organized labor won 80 per cent of the time when it spent money to help House candidates in 1976, but its batting average dropped to .500 when union members tried to influence Senate elections with their political war chest, a Republican Party study says.

Labor's candidates won 80 out of 100 House races where unions donated a considerable amount of money, the study shows. But there were only 20 winners in 40 Senate races where labor contributions were significant.

This analysis of 1976 House and Senate races was made by the Republican National Political Action Committee, an arm of the GOP that is trying get big business to give candidates money for this year's congressional races on a level that would counter labor's millions.

Unions and big corporations are banned by law from giving direct contributions to federal candidates. But both can organize groups to solicit voluntary contributions from members or employees.

The GOP study, based on financial reports filed with the Federal Election Commission, showed organized labor spent at least $10.5 million on congressional races two years ago - and nearly all of it went to Democrats.

Labor's two biggest contributions were spent on losing causes.

William Green, the Democrat who lost to a Senate race to Pennsylvania Republican John Heinz, III, received $245,480 from labor, while Sen. John Tunney, (D-Calif.) got $230,488 but lost to S. I. Hayakawa, a California Republican.

Labor's big winner - and third-largest recipient - was Daniel Patrick Moynihan, a New York Democrat who received $222,488 in his battle with Sen. James Buckley (Con. R-N.Y.). Fourth was Sen. Vance Hartke (D-Ind.) who received $210,754 and lost.

The study also shows labor spent a lot of money on "old friends" with safe seats who probably didn't need the money to win. This category included Sens. Harrison Williams, (D-N.J.) $205,008; Hubert H. Humphrey (D-Minn.) $125,231; Edmund S. Muskie (D-Maine) $77,321; Edward M. Kennedy (D-Mass.) $76,901, and Majority Leader Robert Byrd (D-W. Va) $49,866.

On the House side, 100 candidates received from $23,649 to $106,535 from labor - and 80 won. In several cases, labor spent the money where it was most needed.

Rep. Stan Lundine (D-N.Y.) received the most - $106,535. Lundine's upstate New York district had always been Republican until he captured it four years ago.

The second biggest House recipient of labor funds was Rep. Lloyd Meeds (D-Wash.) who received $67,723. He won re-election by 542 votes and has announced his retirement this year.