A federal grand jury that has been investigating allegations of criminal acts, such as destruction of documents, by key career civil service officials under the Nixon administration has decided against any indictments.

Civil Service Commission Chairman Alan Campbell reported the grand jury's decision yesterday during House hearings on the Carter adminstration's proposals to overhaul the civil service system.

The Justice Department investigation, begun before the Carter administration took office, grew out of a congressional probe and a commission report that revealed that Nixon administration officials had manipulated civil service procedures in order to get federal jobs for politically favored persons.

Still going on is an investigation of administrative, as opposed to criminal, abuses of the merit system within the ranks of the Civil Service Commission, which is supposed to police such practices in other agencies.

The commission last November hired an outsider lawyer, former assistant attorney general Mitchell Rogovin, to conduct that inquiry. Rogovin declined comment yesterday on the grand jury decision but said his own investigators are "working hard" and expect to finish their interviews with CSC staff members this month, and then write a report.

In addition to alleged abuses of the Nixon era, Rogovin is looking into recent charges that senior CSC staff members have obstructed some of the commission's attempts to investigate complaints of racial and sex discrimination, or have failed to take "corrective" action when told of merit system abuses. Those charges were made by the CSC director of equal employment opportunity, Clinton Smith.

Regarding the grand jury decision, 'We're just glad it's over with. When your people are being called before a grand jury, you can't really tell whether they are just giving information or are defending themselves."

The criminal investigation was based on charges, made in the aftermath of the congressional probe, that officials had destroyed or "stripped" some of the files sent to the House committee, the spokesman said.

A Justice Department spokesman declined comment on the grand jury action, adding that all such information would have to come from the CSC.

President Carter's proposals for revamping the civil service system have come under fire, primarily from federal employe union leaders and some members of Congress. They argue that certain elements of the plan would make political manipulation even more likley than it is under the present system.

Campbell maintained during yesterday's hearing that, on the contrary, the proposed legislation would for the first time limit the number of political appointees, spell out specific illegal abuses of merit procedures, set up a performance review board to advise on the evaluation of career executives, and establish an independent, merit protection board and special counsel to represent federal employes interests.

These and other elements of the plan, he said, provide "strong, positive safeguards" against the possibility of politicization.

Changes are needed so that top federal officials can make more effective and efficient use of their work force, according to the administration.

Also yesterday, several members of the House committee indicated to Campbell that they would push for pay bargaining rights for federal employes' unions if Carter holds federal workers to a raise of under 5.5 percent this year.

The president has been considering such a move as part of broader anti-inflation campaign. But union leaders have threatened to withdraw their tenuous support for his civil service reform bill if he does not allow a federal pay raise based on so-called comparability with the private sector - which has been estimated at 6 to 6.5 percent.