The Justice Department's Public Integrity Section reported yesterday that it indicted 1,193 people in public corruption cases last year and obtained 1,027 convictions, but an "extraordinary" amount of the unit's time was devoted to independent counsels investigating Reagan administration officials.

In its annual report to Congress, the section said that in 1986 it conducted preliminary investigations in six cases that led to the appointment of independent counsels. Nine independent counsels have been named since the Ethics in Government Act was enacted in 1978, seven of them during the Reagan administration.

Besides the ongoing Iran-contra investigation, the independent counsel cases involve allegations against former White House chief of staff Michael K. Deaver, former presidential assistant Lyn Nofziger, former assistant attorney general Theodore Olson, former assistant attorney general W. Lawrence Wallace and former labor secretary Raymond J. Donovan. Donovan was the subject of an earlier independent counsel investigation that ended without indictment.

Deaver was indicted earlier this year on perjury charges. And Nofziger was indicted last month on six counts of violating federal ethics laws. The Nofziger investigation was expanded last May to include actions taken by Attorney General Edwin Meese III, and that portion of the investigation is continuing.

The Public Integrity Section, headed by Gerald E. McDowell, conducted another preliminary investigation into financial questions about Faith Ryan Whittlesey, Reagan's ambassador to Switzerland, but Meese decided against requesting an independent counsel in that case.

Under the Ethics in Government Act, the section must conduct a preliminary investigation of no more than 90 days when specific allegations are received from a credible source that a high government official has committed a crime. Unless the investigation finds that the allegations are clearly unfounded, the attorney general is required to ask a special judicial panel to appoint an independent counsel to conduct a full investigation.

The report said the independent counsel investigations "required an extraordinary and unusual dedication of resources" in 1986 that required the section to "curtail" some of its more ordinary cases.

The section said it conducted investigations leading to indictments last year of 596 federal officials, 88 state officials, 232 local officials and 277 other people allegedly involved in crimes.

Among the cases was the conviction of U.S. District Court Judge Walter L. Nixon Jr. of Mississippi on two charges of perjury. He was sentenced to three to five years in prison and becomes the second federal judge in history to be convicted of crimes committed while in office.

The section also assisted the House and Senate last year in the impeachment action against U.S. District Court Judge Harry Claiborne of Nevada, who was the first sitting federal judge to be convicted of a crime.

In Philadelphia, an ongoing investigation into corruption at the Internal Revenue Service led to indictments of nine persons, including three former IRS agents. Since 1981, 20 persons have been indicted; 16 have been convicted and four are awaiting trial.