President Reagan yesterday nominated three men to judgeships in D.C. Superior Court. The nominees are a high-ranking prosecutor, a U.S. Justice Department lawyer and an administrative judge with the Nuclear Regulatory Commission.

They are Reggie B. Walton, 32, executive assistant United States attorney and the highest-ranking black in the prosecutor's office here; Richard S. Salzman, 38, a former Justice Department lawyer who is now an administrative judge and member of the Atomic Safety and Licensing Appeal Panel of the Nuclear Regulatory Commission, and Warren R. (Willie) King, an attorney-adviser for the Justice Department's office for improvements in the administration of justice.

The nominations, if confirmed by the U.S. Senate, will give Reagan a total of five Superior Court appointments, more than a tenth of the 44-member bench after only four months in office. Reagan must now fill a sixth vacancy, created by the elevation of Judge James A. Belson to the D.C. Court of Appeals earlier this week.

Reagan made the selections from a list of 12 names sent to him by the city agency that recruits and recommends local judicial candidates, the D.C. Judicial Nomination Commission. D.C. Mayor Marion Barry, who is seeking White House support for legislation that would give him, rather than the president, authority to appoint city judges, could not be reached for comment on Reagan's selections.

The three lawyers were nominated to fill vacancies created by the retirements of three veteran Superior Court judges, who left the bench earlier this year to enjoy advantageous retirement benefits.

Walton, who was nominated to fill Judge Leonard Braman's seat worked with the Philadelphia Public Defender's office in 1975, according to biographical material released by the White House. In 1976, Walton joined the prosecutor's office here. Among his duties was the job of heading the Career Criminal Unit that prosecutes serious cases involving repeat offenders. In 1979, Walton was appointed to his current position, the third highest-ranking position in the office of more than 160 attorneys under U.S. Attorney Charles F. C. Ruff.

King was selected to fill Judge Fred L. McIntyre's seat, according to the White House statement. King served as an assistant U.S. attorney from 1969 until 1975, taught at Antioch School of Law for three years, then joined the Justice Department.

Salzman also once served, the Justice Department as a trial attorney in the Civil Division. In 1976, he became assistant chief counsel of the Federal Highway Administration, according to the statement. Salzman was named to fill Judge William S. Thompson's seat.

In making his selections, Reagan passed over two women named on the list. Of Reagan's first six local judicial appointments, he has selected two members of minority groups, but no women. Superior Court judges serve 15-year terms.

White House counsel Fred Fielding has said that "competence" is the first consideration in Reagan's appointments to the local bench, a statement that was read by many court observers to mean that more conservative members of the uptown bar were being encouraged to apply.

Many lawyers saw what they perceived as a chance to enter a judicial competition that historically had excluded them. The nomination commission conducted a wide-ranging search that attracted more than 50 candidates, the largest applicant pool in the commission's limited six-year history.

However, the list that the seven-member commission eventually sent to the White House was notable in that it excluded several prominent, more conservative lawyers and prosecutors who many thought had an improved chance of being appointed.