RONALD REAGAN has announced that one of his first acts as president will be to put an immediate "freeze" on the hiring of federal government workers, with the aim of then achieving substantial reductions in the federal work force through normal attribution. Although the president-elect did not specify how many workers he hoped to get off the payroll, one transition aide suggested that a cut of around 200,000 might be sought.

Could it be done? Most people are unaware that, despite the substantial growth in the size and complexity of government programs in recent years, the permanent federal work force has actually been shrinking, not growing. In 1970 there were about 1,987,000 full-time permanent workers in the federal civilian work force, excluding the now independent Postal Service. As of September 1980, 10 years later, there were 1,866,800.

Most of the job drop-off during the Nixon and Ford administrations reflected post-Vietnam reductions in Defense Department civilian employment partially offset by job growth in the Veterans Administration (the biggest gainer), HEW, Treasury and Justice. In fact, throughout this decade there has scarcely been a period in which some sort of hiring limitation was not in force. One of the longest continuous periods of "partial freeze" is under way right now. As part of his mid-March budget cuts this year, President Carter imposed a new set of hiring limitations -- the third of his term -- that has led to a drop over the past five months of about 21,000 regular government workers.

You don't have to be in favor of an overblown bureaucracy, government waste or any of the rest of that pernicious gang to observe that a policy of reducing personnel by not replacing people who quit can quickly lead to a top-heavy and otherwise unbalanced work force. This is because normal tornover among government workers tends to occur mostly among the lower ranks of service, clerical and secretarial personnel as well as among junior professionals. There is also a general, although by no means universal, tendency for the best and the brigtest workers to be among the most mobile. Part-time and temporary workers, whose number has been growing, could be cut, but such workers have primarily been hired either to cut backlogs in important claim and audit functions or as part of the effort to increase employment of women, minorities and the handicapped.

There are other limitations to be condiered as well. About 46 percent of federal civilian workers are employed by the Defense Department, an agency slated for big program increases. Over 20 percent more are in the Veterans Administration, Treasury, Justice, the Federal Aviation Administration, the various Inspector General offices and the Coast Guard -- all either agencies with essential enforcement or service activities or highly popular programs. If you add to this the 80,000 Social Security workers, most of them in field offices already working substantial overtime, you are left with only about 520,000 workers to do the rest of the government's work and to sustain the full force of further cuts as well.

Our sense of it is that if Mr. Reagan wants also to maintain and improve the efficiency of federal programs, while limiting the size of the work force, he should probably at least consider a more selective (and more difficult) approach. This would be to relate further work force cuts to actual reductions in government functions and then to reassign the released personnel to those areas that are already understaffed. If he should also want to salvage what is left of government-worker morale after 10 years of unrelenting pressure, he might consider a "defreeze" -- thaw? -- of another sort: turning the warm water back on in government bathrooms.