President Carter's unhappiness about the large numbers of government workers drawing "excessive salaries" and excessive benefits" could trigger job cuts and promotion freezes here, where 347,000 people work for Uncle Sam.

When he met with the Cabinet Monday, the President said that he was worried about the high pay and fringe benefits going to so many government workers, and the large number of top-paid employees against assigned to headquarters. That means here.TCabinet officers weren't given any specific directions to reduce the nmber of high-grade employees. But the president said that anytime they have the opportunity, they should cut down on the number of people in the top layers of their operations.

Most government agencies are headquarters here. That power and command struct utre - coupled with the high pay of members of Congress and political appointees - makes the average white-collar government salary in the Washington aarea just over $19,000. Outside of Washington, the average white-collar federal civil servant averages $16.130.

Federal officials do not anticipate any move to lay off large numbers of top paid government executives as a result fof the President's statement to the Cabinet. But on the other hand, they don't know what Cabinet officers will do, or how they will take Carter's comments.

Some officials may translate Carter's Monday tatstements about "excessive" salaries and benefits into command, and try to cut the number of top jobs using the on-going 3-for-4 job freeze. Under that plan, agencies have been told to reduce employment by hiring only three replacements for every four vacancies that occur.

There are no jobs or grade restrictions in the semifreeze. Agencies may replace whomever they wish so long as they stick with the 3-for-4 plan. Some, however, might decide to meet the President's top-job cut back by replacing lower-grade workers as they leave while leaving upper-gade jobs open. That can bring the average pay and grade structure down rather quickly, just as it can slow promotion's nd cause morale to sag.

"We don't know what to make of it (the President's statement) yet," a top manpower expert said. "But I wouldn't be surprised to see some upper-gade jobs left vacant, and maybe even a move to shift more operations" away from Washington.

Health, Education and Welfare workers who have - for good reason - fears about massive downgrading plans may be in for temporary relief. Secretary Joseph Californo is planning to slap a 90-day moratorium on any downgradings tht might result from administrative reorganization. Califano made the pledge to Kenneth T. Blaylock, president of the American Federation of Government Employess in a meeting yesterday.

Meantime, HEW may go to the Civil Service Commission and ask for a similar freeze on downgradings that are slated because of desk audits of jobs. HEW has 36,000 workers here and preliminary studies indicate that many jobs in the Grade 12 through 15 level are overgraded.