A special House subcommittee yesterday waded further into the sticky details of President Carter's welfare plan, including the troublesome question of whether the plan is fair to both rich states and poor.

Rep. William Clay (D Mo.) wanted to know why California, with about 11 per cent of the nation's welfare recipients, would get $130 million, or 21.6 per cent of a S600 million pool of emergency assistance money in the first year of the program.

He didn't like the explanation - the emergency assistance money would be allocated during the first year on the basis of which states now spend the most overall on welfare and that over the next four years that funding formula would shift so that the money would be handed out on a welfare population basis.

"Why should we perpetuate injustices in the present law?" Clay asked. "The formula needs to be fair."

As Carter's plan is written now, Missouri would get S7.7 million of the emergency aid in the first year. But by the fifth year, Missouri's share would rise to S13.2 million, while California's would drop to S60.2 million.

In this second day of an anticpated month of day long debates, several members questioned whether the subcommittee can stick to tis original timetable of shaping a bill by Christmas, and voting on it in January.

Rep. Augustus F.Hawkins (D.Calif), who has raised a series of questions about the jobs portion of Carter's plan, said the President needs to make decisions about tax revision, urban policy and renewal of the CETA (Comprehensive Employment and Training Act) program before a new welfare plan can be intelligently debated.

"I think we're wasting our time until we know what his overall economic plan is . . ." Hawkins said. He predicted it would take the subcommittee two to three months to agree on a new form of welfare.

Clay voiced similar thoughts, Rep. William M.Brodhead (D.Mich) said he foresees ". . . a tremendous shakings out period once the administration realizes this bill is going to be radically altered, almost built again from the ground up. I think the majority of the committee agrees with that."

The subcommittee is scheduled to meet for half an hour today with President Carter. Chairman James C.Corman (C.Calif), who has publicly committed himself to trying to report out a paln close to Carter's, said Carter "wants to cooperate with us, I thought it a useful thing to do."

Other issues raised yesterday included:

Should the plan allow an earned income tax credit for families making up to $21,000 a year, as Carter proposed? (Only very large families of seven or more would be eligible for aid at that income.)

Should the plan allow states to impose a residency requirement, and therefore exclude migrant workers, as it does in its present form?

Should some illegal aliens be eligible for welfare while others aren't, which is the case as it is now written.

Does the plan work against Carter's belief that persons "living in sin" should get married? Under present law, administration staff members said, a woman on welfare with two children can marry a man with money and her children will remain eligible for welfare because the law does not require her new husband to support them.

Carter's plan would make the children ineligible as well. Brodhead said that might be "a powerful disincentive" for some people to get married.

More discrepencies between the administration's cost estimates over those of others also came to light.

A study done by California indicates that Carter's plan will cost S348 million more in state and local funds than is spent now.

The administration's cost estimates predicted California would save $400 million in state and local costs under the Carter plan.