Secretary of Health Education and Welfare Joseph A. Califano Jr. told Congress yesterday the administration is not abandoning its bill to restructure the welfare system and said he strongly opposes a less costly substitute sponsored by Rep. Al Ullman (Dore.).

Califano's statements came as a special House welfare subcommittee scheduled a vote today on whether to kill the Carter plan and adopt Ullman's substitute instead.

Califano, in a personal appearance before a Senate welfare subcommittee and then in a letter to House subcommittee chairman James C. Corman (DCalif.), said the Ullman plan is "less efficient and less equitable in achieving the goals of welfare reform."

Ullman, however, in a statement to the House subcommittee, called his plan "responsible. . . achieveable either in full or in part," and said of welfare "reform" that "it passed all at once." The Carter proposal is "more than the budget can take," Ullman added.

Both bills provide for a $4,200 annual welfare benefit for a family of four consisting of a mother and three children with no other income.

But the Ullman bill is less generous to families where both parents are present. It provides only 500,000 public service jobs a year for welfare clients able to work.The administration bill has over a million. The Ullman plan also would not enlarge cash assistance as Carter's would to cover single persons and childless couples. And Ullman would retain the food stamp program for families with children, while Carter would merge it into welfare.

Instead of relieving the states of about $3.4 billion in welfare costs, Ullman's alternative would provide only about $1.1 billion in fiscal relief.

The Ullman bill is estimated to cost $8 billion more than existing programs in 1982, the first full year in effect. By contrast, the administration bill as amended so far would raise costs about $21 billion. Ullman indicated he believes his bill would be far more likely to overcome conservative congressional opposition to added welfare spending, particularly in the Senate.

Some of that opposition surfaced in the Senate subcommittee yesterday when Carl T. Curtis (R.-Neb.) asked Califano, (Can you explain to me why you have found it impossible to design a welfare program which doesn't add" $15 billion to $20 billion to existing costs?

Curtis added, "I believe when the American people hear the president talk of welfare reform, they think he's talking about fewer tax dollars, fewer people drawing welfare," not more money and bigger welfare rolls.

However, subcommittee chairman Daniel P. Moynihan (D-N.Y.), a supporter of the Carter bill, called it "one of the most important pieces of social legislation in history," which would care for the needy and protect the most impoverished persons in society from destitution.

Many believe that the bill's chance of final passage in both chambers this year is slim, but Moynihan said, "Reports of the demise of the president's program are greatly eyaggerated."

Califano told the Senate subcommittee that the administration will support special welfare "fiscal relief" payments to the states of $450 million in fiscal 1979 and $525 million in fiscal 1980 to be authorized as part of the welfare bill to help push it through. The relief amounts would be for the years before the new welfare program goes into effect.

Califano also said computer comparisons of welfare payments to parents and dependent children in 24 states and the District of Columbia showed 13,584 recipients had received illegally in more than one state.

The Corman subcommittee in the House is expected to defeat the Ullman substitute today, perhaps narrowly, and approve the administration bill with minor revisions.