Republican national chairman Richard Richards predicted yesterday that the GOP would win control of the House of Representatives in 1982, aided by the defection of some conservative Democrats who support President Reagan's economic program.

Democratic congressmen who support Reagan's tax program, as 63 of them did his budget plan, will be out of favor in their own party, Richards said, and will be actively encouraged to join what he now foresees as a coming Republican majority.

The last congressman to leave the Democratic Party was John Jarman of Oklahoma, who joined the Republican in 1975 and subsequently retired. The seat has remained in Republican hands.

The Republican Party has not controlled the House since the 1952 elections and in 1954 Democrats regained control.

Richards acknowledged that GOP success in the next election was largely tied to continued public approval for President Reagan, and particularly to the success of his economic program.

"If he does well, we take off like a rocket," Richards said. "If he doesn't, we slip back to where we were."

If Reagan's economic program does not succeed, the GOP chairman continued, voters will conclude again that there is "no difference" between the parties, a situation which benefits the majority Democrats.

richard's optimism was based partly on the population shift to western and southern states, where Republicans are in the ascendancy. The national committee is participating in a well-financed GOP campaign to draw the new congressional boundaries because of the 1980 census and redistricting so they are more favorable to Republican candidates than the Democratic-favoring districts drawn in 1971.

When legislatures refuse to redraw the lines, Richards said, the GOP is prepared to make court challenges.

Richards said that 1980 had the promise of being a watershed election, comparable to what 1932 was for the Democrats.

He discounted the impact on the election of emotional social issues and independent expenditure groups such as the National Conservative Political Action Committee. Richards said the election was a reflection of the trust of a majority of Americans in Reagan's leadership coupled with a feeling that the Democrats no longer had the answers to the nation's problems.

He said that Reagan's coattails had continued after the election, attracting more money and better candidates to the party with results that would be evident in the 1982 election.

The GOP chairman's optimism was darkened only by the timing of Reagan's proposed Social Security reductions, which he said he had learned about only when they appeared in the newspapers.

"It was not the most opportune time," Richards said. "We would have been better to wait."

He said that the cuts would be unpopular with those just approaching early retirement age because their benefits would be reduced. Other Americans, he said, would wind up believing that they would be better off having a smaller payment if the system is on a sound basis.