The Republican-controlled Senate last night gave, 50 to 49, provisional approval to its compromise with the White House that would halve budget deficits within three years, largely through deep new reductions in domestic spending.

The victory for President Reagan and the Senate Republican leadership came only after concessions to dissident GOP senators and was largely symbolic. It could be reversed this week in a series of votes on individual items in the package.

Several senators who voted in favor yesterday say they intend to vote against critical but controversial components of the package, such as defense spending increases and a cutback in cost-of-living increases for Social Security.

One, Sen. Mark Andrews (R-N.D.), called the plan a "turkey" but said he supported it because of concessions already made and others that he expects the leadership to offer in hopes of keeping the plan from unraveling.

In a statement issued by the White House, Reagan said the vote "demonstrated foresight and responsible leadership" and warned that supporters "will have to stand fast against a long list of amendments."

After days of intense negotiations with wavering Republicans, Majority Leader Robert J. Dole (R-Kan.) won his biggest test since he captured the Republican leadership post earlier this year. He kept in line all GOP senators except Charles McC. Mathias Jr. (Md.) and Robert W. Kasten Jr. (Wis.).

Sen. John P. East (R-N.C.) is ill, and Vice President Bush was on hand to cast a tie-breaking vote, if needed.

Mathias has been holding out for repeal of tax indexing, and Kasten seeks restoration of funds for several programs, including Export-Import Bank loans and urban development action grants, both of which would be terminated under the plan. Democrats voted against the plan.

The vote occurred after a day of partisan guerrilla warfare over Social Security in which frustrated Democrats complained of "hardball" GOP tactics in denying them a vote to scuttle the proposed cutback. Cost-of-living increases would be cut from 4 to 2 percent over three years.

The flare-up came as Republican leaders put out feelers for bipartisan cooperation on a compromise if the plan starts to unravel on item-by-item voting expected to begin today.

Angry Democrats warned that the GOP jeopardized chances of such cooperation by closing them out of early action on the plan, especially maneuvering over Social Security.

"It's not helping the process if we see the majority using its powers to the extent that it's abusing its power," said Sen. Lawton Chiles (D-Fla.), ranking Democrat on the Budget Committee.

Since the budget debate opened nearly a week ago, Democrats have been pushing for an early vote on their proposal to "save" the cost-of-living increase.

But Dole, scrambling for enough Republican votes to get the plan past its first hurdle, promised dissident GOP senators the first crack at an amendment to restore full funding of the Social Security adjustment.

This would mean that, win or lose on the amendment, Republicans will have led the charge for Social Security, insulating them from Democratic charges that the GOP is an enemy of Social Security.

In an attempt to foil an intricate parliamentary maneuver engineered by Dole to assure Republican control of the amending process, Democrats surprisingly tried what was described as a "last-gasp" effort to force a vote on their proposal.

But Dole kept Republicans in line, even those who plan to vote against the Social Security cutback, and the proposal was defeated, 54 to 45, basically along party lines.

As Democrats then proposed a nonbinding "sense of the Senate" resolution on the issue, Dole observed sardonically, "I can see we're ginning up the PR machine to see who can protect the senior citizens the most."

The Republican compromise, hammered out by Senate GOP leaders and top White House officials last month, proposes cutting deficits by almost $300 billion over the next three years, starting with $52 billion next year.

The goal is deficits of no more than $100 billion by fiscal 1988, or less than half of the $200 billion-plus deficits that would otherwise occur during the period.

For the next fiscal year, the proposal would cut domestic spending by about $30 billion, while increasing defense spending by $15 billion, less than half of what Reagan seeks.

Domestic savings would be made by eliminating or phasing out nearly 20 programs ranging from the Amtrak rail-passenger service to the Job Corps, and drastically cutting about 30 others, such as Medicare, farm supports and student aid.

In many cases, the cuts are deeper than previous Reagan spending reductions, including the landmark retrenchment proposals of his first year in office.

Almost as controversial as the Social Security proposal is the proposed increase in defense spending to 3 percent above inflation, half of the nearly 6 percent Reagan sought.

Many members of both parties have argued that defense spending should be cut more because of the huge military buildup of the last four years. The Defense Department has $52 billion in unexpended funds and giving it more is "like force-feeding a goose," Sen. Ernest F. Hollings (D-S.C.) said during yesterday's debate.

Faced with at least 68 proposed amendments, Dole was privately discussing concessions with Republican senators for support on specific program votes and sending signals of compromise to Democrats in case the package falls apart.

"I would hope that, when all this preliminary maneuvering is over, there will be a majority on both sides willing to sit down and talk and work out a package," he said.

"There will be a new package at the end, win or lose on this [the preliminary vote]," Finance Committee Chairman Bob Packwood (R-Ore.) said.