Senate Judiciary Committee members questioned yesterday whether President Reagan's choice to head the federal Office of Juvenile Justice and Delinquency Prevention is qualified for the job and committed to the program.

But acting Director Alfred S. Regnery told the committee that his inexperience may be an advantage, and he promised to carry out the law if funds for the program continue to be appropriated.

If Regnery is confirmed by the full Senate, he will take over a $70 million program that the administration has tried unsuccessfully for two years to kill.

Sen. Howard M. Metzenbaum (D-Ohio) asked why Regnery, who has virtually no experience in the juvenile justice field, should be considered qualified for the job.

"I don't see why you should be head of the program more than any other of the other 215 million Americans . . . . Why you? What . . . qualifies you to head this department instead of Mr. Jones, Mr. Smith or Mr. Anybody?" Metzenbaum asked.

Regnery, who worked in the Justice Department's Lands and Natural Resources Division before his new appointment, said, "I am a lawyer . . . . I am a fairly good administrator. I have certainly a very open mind about issues. I have studied criminal justice matters very carefully."

But when Metzenbaum demanded to know of a single book or reference he had studied, Regnery said he would have to check the titles in his office.

Regnery said he believes he his lack of experience in juvenile justice may be a benefit, enabling him to "challenge some of the orthodoxy and look at things from a different point of view."

"The statute will be carried out--that's as much as I can say about it--if the money is appropriated," he said.

Regnery, a former official of Young Americans for Freedom and assistant to Sen. Paul Laxalt (R-Nev.), also was questioned about charges that he is attempting to change the program's direction from juvenile delinquency prevention and rehabilitation and toward apprehension and punishment.

In response to questioning by Sen. Arlen Specter (R-Pa.), who heads the subcommittee on juvenile justice, Regnery said he believes that "virtually everything we do bears on delinquency prevention.

"If you prosecute someone and put them in an institution and prevent another delinquent act, that's prevention . . . ," he said.

Regnery said he believes that other departments in the federal government are putting extensive resources into programs that deal with delinquency and that his small budget can have much additional impact.

But Specter said the law "specifies in unequivocal terms that a prime objective--perhaps the main objective--of the statute is crime prevention."

Regnery also was questioned by Chairman Strom Thurmond (R-S.C.) about allegations that a number of grants have been cut because of a "hit list" of programs and individuals circulated by some conservatives.

"I've never seen that hit list," Regnery said. "I heard about it ever since I came to the Office of Juvenile Justice . . . . I don't know who's on the list. I can't comment on whether they've been cut off."

He was also asked about reports that his car bears a bumper sticker saying, "Have You Slugged Your Kid Today?"

Regnery said he considers the sticker to be a joke, adding that he also had a "Nuke the Whales" bumper sticker in his Justice Department office.