President Reagan's controversial nomination of Alfred S. Regnery to head the Justice Department's Office of Juvenile Justice and Delinquency Prevention was approved yesterday by the Senate Judiciary Committee and sent to the Senate.

After meeting privately for 45 minutes to discuss a confidential report on an FBI investigation into Regnery's background, the panel approved the nomination without debate, 11 to 3.

The White House had placed the nomination on hold last month while the FBI investigated charges by William Ylitalo, a Madison pediatrician, that Regnery would pose "a danger to the health needs of our children."

Ylitalo, who based his charges on Regnery's behavior during the 1975 birth of one of his children, was interviewed extensively by the FBI. The results of that investigation have not been made public.

Regnery, who has been serving as acting director of the office since November, also has been criticized because of his plans to shift the emphasis of the office away from delinquency prevention and toward stricter punishment of serious offenders.

The White House has urged in past budgets that the office be abolished. Regnery, a former aide to Sen. Paul Laxalt (R-Nev.) and an official of the Young Americans for Freedom, was chosen to head the office after it became clear that Congress would not delete the program's $70 million in annual funding.

Sen. Joseph R. Biden Jr. (D-Del.), who voted against Regnery yesterday, said his objections "do not at all relate to the personal allegations. They're irrelevant. They do relate to whether or not he's committed to the mandate of Congress" in running the program.

Biden said that he is concerned about Regnery's lack of experience in the juvenile justice field. "His emphasis on detention as opposed to prevention is misplaced . . . ," Biden said. "His assumptions as to how the agency should be run are different from the congressional mandate."

Biden also criticized Regnery's role in giving initial approval to a grant proposal for a book on juvenile justice to be compiled by a staff aide on a Senate Judiciary subcommittee. Justice officials blocked the contract when they learned that it included a provision under which Regnery was to be paid $1,000 to write one chapter.

Biden called Regnery's behavior "improper," and said that he exhibited a "lack of sensitivity . . . . It's a reflection of his lack of experience, his lack of administrative capability.

"But in fairness to Mr. Regnery, I think he's in a position where he's attempting to carry out the Reagan mandate, which is to dismantle" the program, Biden said. "Mr. Regnery is just following orders."

Biden predicted that the Senate would confirm Regnery "rapidly" because of his support from Laxalt, a close adviser to Reagan.

The other senators opposing the confirmation yesterday were Howard M. Metzenbaum (D-Ohio) and Max Baucus (D-Mont.).