A Senate Finance subcommittee yesterday began hearings on a Republican alternative to President Carter's stalled welfare bill.

Sen. Henry M. Bellmon (R-Okla.), one of its sponsors, said the legislation would raise welfare costs only $8 billion a year instead of the Carter bill's $2 billion, and would also provide $3 billion a year in fiscal relief for states and localities instead of the $2.2 billion provided by the Carter bill as amended by a special House subcommittee.

And Bellmon said the GOP measure would do this without significantly enlarging the bureaucracy, wiping out food stamps or creating a large number of new public service jobs.

Senate Minority Leader Howard H. Baker (R-Tenn.) said a better system must be devised because "the most explosive social issue in the U.S is the simmering resentment that the working population has against abuses of the welfare system." Baker is a cosponsor of the legislation, as a Democrat Abraham A. Ribicoff (Conn.).

Subcommittee Chairman Daniel P. Moynihan (D-N.Y ), a sponsor of the Carter bill, gave the Bellmon bill an extremely friendly reception. He called it "a very important option before this committee" and something that deserves the most serious consideration if the Carter bill can't move. Prospects for the president's proposal are clouded by its big price tag.

Moynihan also got in some comments on the "craziness" of the current welfare system and the "mentality" of the Department of Health, Education and Welfare - one of his favorite punching bags - after he heard the following testimony:

Dr. Blanche Bernstein, welfare administrator of New York City, daid that "theoretically it is possible" for a welfare mother with three children there "to earn as much as $29,000 a year and still receive= up to "a couple of hundred a year" in welfare benefits by pyramiding decuctions for child care, work expenses and other exclusions from income. She also said the Carter bill will give New York City only $66 million in fiscal relief annually on welfare costs of about $556 million, compared with $108 million under the Bellmon bill.

Keith Comrie, director of the Los Angeles County Department of Public Social Services, said that if all the papers that must be handled in processing a welfare payment were pasted end-to-end, they would be 70 feet long.

Moynihan, railing against bureaucratic papershuffling, delcared, "We have taken to calling Hew 'the thing.' It's cut there and it's out to get us all."

The Bellmon bill differs sharply from the Carter plan in preserving food stamps for welfare mothers, leaving administration in state hands, and paying $1-an-hour subsidies to private employers to hire welfare clients instead of creating an equivalent number of federally funded public service jobs.

Here are key feature as outlined by Baker and Bellman:

States would be required to pay welfare mothers and their families (and unemployed fathers, too, where they were present in the home) an overall benefit in cash and foot stamps equal to 55 percent of the poverty line in 1981 (it's currently $6,200 for a family of four); this would rise to 65 percent by 1985.

The federal share of the total welfare payment would rise from the current range (50 to 83 percent) to a minimum of 80 or 90 percent by 1982, but only on payments up to the poverty line. States alone would pay for anything above that.

Baker-Bellmon would create 375,000 public service jobs for welfare clients who can't find private employment, instead of Carter's 1.1 million. It would give private employers a $1-an-hour tax credit or direct subsidy for each welfare client they hire at the prevailing local wage in addition to their normal workforce.