A Senate bill to aid the housing industry by subsidizing mortgage interest payments for buyers of new homes was abruptly pulled back yesterday by its two chief Republican sponsors who said they feared it would be weighted down with Democratic amendments that would make it unacceptable to President Reagan.

Sen. Jake Garn (R-Utah), chairman of the Senate Banking Committee, and Sen. Richard G. Lugar (R-Ind.), chairman of the housing subcommittee, canceled a markup session on the legislation just as it was to begin, saying they lacked the votes to head off a string of Democratic-sponsored "budget busting" amendments.

"Having a loaded up bill that doesn't pass doesn't do anyone any good," Garn told a news conference.

Lugar, the author of the bill, said there is widespread support for aid to the ailing homebuilding industry, "but it is not going to happen in a Christmas tree fashion."

The bill has no opponents, Garn said. "Everyone just wants to sweeten it and add things to it."

He said the Lugar proposal would be difficult to steer through the House and Senate and past the president even in its present form. "If it was loaded up, it would have no chance," he added.

Lugar said the White House is taking a "wait-and-see attitude" toward the bill, which would cost $1 billion its first year at a time when the administration is seeking ways to hold spending down.

"My own judgment is that we could activate this very modest program without doing violence to the president's econonmic recovery program," he said.

The Lugar bill, with 31 cosponsors, would provide a partial interest subsidy for new home buyers with annual family incomes under $30,000. Qualified buyers would pay an interest rate 4 percentage points below the FHA rate, now 15.5 percent, for five years. Buyers would have to repay the subsidy when their homes were sold or refinanced.

Supporters estimated the proposal would cost $5 billion over five years. It has been attacked indirectly by Reagan and opposed by realtors.

Lugar was especially critical of two Democratic alternatives, supported by some Republicans on the Banking Committee. One would provide that 30 percent of the subsidies would go to purchase existing homes; the other would raise the eligibility requirements to 145 percent of median income in any area.

Lugar maintained that this would dilute the job creation aims of his proposal and make high income families who don't need help eligible for assistance.

Another amendment, also troubling to Lugar, would raise limits on eligible mortgages from the $67,500 in his plan to $91,240 in some high income areas.

The Democratic package also includes down payment assistance for first-time homebuyers, special subsidies for family farmers and aid to families who have lost their homes because of unemployment.

Lugar said he would refuse to negotiate on any of these items. This angered Democrats. "It sounds like they're saying if they can't have what they want they're going to take their bill and go home," said one Democratic staff member.

Garn canceled yesterday's session as lobbyists, spectators and reporters jammed the hearing room waiting for it to begin. They called a press conference an hour later.

"Sen. Garn and I are blowing the whistle on the whole thing and saying 'school's out,' " Lugar said.