The Reagan administration yesterday proposed restoring some of the tax relief it cut last Thursday from the president's business tax-cut program -- a move designed to stem possible business defections over last week's action.

Although all sides stressed the newest revision was only tentative, it was laid out before business groups on the understanding that the administration would embrace the new changes if business returned to the fold.

Unofficial calculations showed the revisions would restore as much as $15 billion between 1981 and 1986 -- or about 30 percent of the $50 billion that last week's proposed cutbacks would have sapped from business' tax relief.

Initial reaction from business groups, though guarded, appeared to be favorable, with corporate leaders mollified if not entirely pleased by the final result.

The peace offering to business came as the House Ways and Means Committee prepared to begin drafting the tax-cut bill Wednesday, possibly with the business portion of the tax reduction first on its agenda.

Although sources cautioned that the schedule could change, panel Chairman Dan Rostenkowski (D-Ill.) was said to be considering taking up the business tax cuts first to buy more negotiating time for the rest of the tax-cut package.

Rostenkowski was angered by the administration's surprise decision last week to abandon earlier compromise talks and forge a conservative coalition instead to work for enactment of the president's latest plan.

Committee strategists hinted yesterday that the chairman may try to stretch out the mark-up session in an effort to splinter the president's coalition and buy time for the Democrats to try to lure supporters to their own alternative bill.

"Time is on our side," one Democratic planner said.

Reagan administration strategists say they believe they can muster a majority made up of Republicans and conservative Democrats.

Democrats on the Ways and Means Committee have outlined a two-year version of Reagan's tax-cut bill that also would provide added relief for taxpayers in the $20,000- to $50,000-a-year brackets, who make up the heart of the electorate.

The proposed changes the administration floated yesterday would involve speeding up the timetable by which its new faster depreciation write-offs for equipment purchases are phased into the tax code.

Under Reagan's earlier depreciation proposal, firms would have been allowed to write off the cost of structures in 10 years, equipment in 5 years and vehicles in 3 years instead of the prolonged schedules now in effect.

However, the plan would have bloated the budget deficit, particularly in fiscal 1982 and 1983. The measure included a proposal to allow buisnesses to use a 200 percent declining balance, that is, doubling its rate of depreciation, in figuring equipment write-offs.

Last Thursday, in an effort to mollify deficit-conscious southerners, the administration announced it was cutting back its plan to push depreciation for structures to 15 years and to slow equipment writeoffs significantly.

Yesterday the Treasury floated a plan that would maintain last Thursday's proposed schedules through 1984, but allow businesses a 175 percent declining balance in 1985 and a double balance in 1986 and later.

It was not immediately clear whether the administration ultimately would backtrack on the depreciation rules for structures as well, although sources said the issue was "under discussion."

The developments came as, separately, the administration unveiled proposals for the first two packages of long-promised spending recissions. But the cutbacks were small ones -- together saving less than $500 million this year.