The Senate yesterday refused to kill the Social Security financing bill, and tentatively endorsed a plan to impose a bigger tax increase on employers than employees.

The attempt to kill the bill by recommitting it to the Senate Finance Committee until next February was made by Henry L. Bellmon (R-Okla.). He said members need more times to study the massive tax increases proposed for both companies and workers. The bill would raise taxes for all workers and more than double them for the highest paid over the next decade. The House has already passed a bill raising workers' taxes even more.

The Senate shot down Bellmon's amendment, 54 to 36, after Majority Leader Robert C. Byrd (D-W.Va.), Finance Chairman Russell B. Long (D-La.), floor manager Gaylord Nelson (D-Wis.), Minority Leader Howard H. Baker (R-Tenn.) and Carl T. Curtis (R-Neb.) all said new taxes are needed now to save the system from bankruptcy.

Curtis opposed killing the bill even though he had just lost, 49 to 41, on an attempt to wipe out the provision that, for the first time, would shift a heavier portion of the Social Security tax load onto businesses than is paid by employees. Since the start of Social Security in 1935, employers and employees have always paid the same taxes. Curtis may try again to kill this provision, which was sponsored by Nelson and backed by administration. By loading extra taxes onto businesses, the Nelson provision allows smaller increases for workers.

Before the vote on Bellmon's motion, Bob Dole (R-Kan.), Barry Goldwater (R-Ariz.) and John G. Tower (R-Tex.) threatened a filibuster to stop the bill unless they got a chance for an up-and-down vote on an amendment - already passed by the House - removing altogether the present $3,000 limit on what a Social Security recipient can earn from a job without reduction or loss of benefits. The administration strongly opposes the amendment on cost grounds. Dole received assurances late in the day from Senate leaders that he would get an up-or-down vote. However, a filibuster by other opponents still was possible.

In opposing Bellmon's motion to recommit, Long and Byrd said the real issue isn't the need for added study but the fact that members are afraid to vote huge new taxes, even though the system needs them to avert bankruptcy. Byrd predicted they will be even more afraid next year, an election year, and will want another postponement until 1979, putting Social Security in a dire financial condition and blocking President Carter from formulating his new tax program because he won't know how large Social Security taxes will be.

Long shouted, "If anyone here can tell us there will be some increase in political courage in the next three to four months, then I'd say wait . . . but knowing what the political realities are, I know that the nearer every member gets to the election, the harder it gets to vote new taxes." He said that because of certain formula miscalculations and economic changes, the system was in a huge financial hole, would have to start paying benefits with "hot money" in a year or so unless massive new taxes were voted.

Nelson said that while the new taxes in the Senate bill don't trigger in until 1979, other provisions save money next year. "The actuaries tell us if we wait until March, the additional cost to the fund will be $1.2 billion."

Bellmon complained that the bill was brought to the floor earlier this week without a committee report to explain it, without even a final text, and said, "This may be a wonderful bill, but why rush it?"

Vice President Mondale was in the chamber buttonholing his former colleagues to make sure the bill was safe.

Early in the day, the Senate approved, 68 to 20, an amendment by Thomas J. McIntyre (D-N.H.) forbiding the government to reduce any veteran's pension because he was receiving Social Security too, and received a Social Security benefit increase. The amendment would cost the government $200 million a year if accepted by the House.

Curtis came close to killing one of the major innovations in Nelson' bill - the provision taxing employers on a larger portion of a high-income worker's salary than the employee pays taxes on.

At present the worker and his employer both pay 5.85 per cent on the first $16,500 a year of his earnings. Nelson's bills, as approved by the Finance Committee, would raise the maximum amount of earnings on which the employer must pay taxes to the first $50,000 of a worker's salary from 1979 to 1984, and then $75,000.