The Senate welfare subcommittee gave Labor Secreatary Ray Marshalla grilling yesterday as he appeared to disclose a bit more about the Carter administration's welfare revision program.

Marshall talked for the first time about one of the administration's specific goals, saying the creation of roughly 1.5 million jobs "might be able to reduce the welfare rolls by 20 per cent . . . That's our rough estimate."

He also opened the door to a possible limited trial run of the new welfare program in one or more states "if, when we collect all the evidence we can, we've got serious doubts. . ." that it will work.

And he said that while details haven't been worked out, "undoubtedly" the Labor and Health, Education and Welfare departments will share administration of the program, with Labor running the jobs portion. President Carter has said he will send his complete set of welfare proposals to Congress in August.

Marshall got into trouble with the subcommittee when he began talking about jobs. Although Chairman Daniel P. Moynihan (D-N.Y.) praised Marshall's opening statement, saying "there's no doubt in my mind that you are on the right trac?," the former U.N. ambassador led the attack.

Moynihan, a consultant on welfare reform for President Nixon, was skeptical about the types of possible public service jobs. Marshall mentioned for welfare families - weatherizing the homes of the poor, removing lead paint from slum housing, and building trails in national parks and forests.

"The jobs are always those the upper middle class thinks should be done," Moynihan said. "Weatherization of low-income homes is certain to be a hit in Georgetown . . . but weatherization is first of al carpenter's work."

"You don't have to be a skilled carpenter to do this," Marshall replied.

"You'd better be if you're on a 14-foot ladder," said Moynihan. "I'm just saying watch it when you decide what is chic for the poor to do this season."

The senator had similar questions about the removal of lead paint. How many jobs could be created to do that? Is it difficult work? Does it involve using a torch, and can someone learn it without burning down the house? Will it involve one crew putting on lead paint so another crew can remove it?

Marshall had not brought with him the specific answers to most of those questions, and Moynihan asked him to send the subcommittee a memo on them. "We are friendly," he kept telling the secretary.

Moynihan asked Marshall how dangerous an occupation forestry was. Marshall didn't know. "Find out," said Moynihan.

He also peppered Marshall with questions about what he called "the variation in language coming from the executive branch."

Senate Finance Committee Chairman Russell B. Long (D-La.) urged Marshall to look for jobs where the poor can help each other.

He said he didn't want the administration "letting all those retired teachers hog up all those jobs in those day care centers at $10,000 a year," when for not much money two welfare mothers could be put to work, and they could bring their children with them.

The public service jobs Labor is thinking of creating, Marshall had said, would pay at or near the minimum wage, or around $5,200 a year.

"You're not going to put Mama to work collecting garbage in New York City," Long said. "For one reason, that job is a 15,000 one and they're not going to let Mama in. It pays too much."

"There are some states that pay more for a family of three on welfare than you're offering in jobs," Long said. "My guess is in some of these high payment states you'll run into a very severe protest from some badly spoiled people..."

He urged Marshall to cut or eliminate welfare payments to those who do not accept available jobs. Marshall said details of a work requirements have not yet been worked out.