While television and all-news radio reports spoke somberly about the cataclysmic prospect of a federal shutdown yesterday, government workers around town held Christmas parties and toiled at their normal holiday season pace.

Most federal employes, when questioned at midday yesterday, said they're accustomed to the almost annual pageant of budget appropriation snags threatening a government shutdown.

For many of the country's 2.1 million nonmilitary federal workers, it was a day for waiting to see whether President Reagan would send them home by vetoing the budget agreement -- but not a day for getting too upset.

"Nobody's worried," yelled a woman running from the Department of Commerce yesterday afternoon. "They're not talking about the budget, honey. Everybody's working."

"It ain't nothing to worry me," said Kevin Willis, a Veterans Administration clerk-typist. "The only thing going on this year is Christmas parties."

In front of the Treasury Department, federal employes continued apace their planting of evergreens. "No one has mentioned getting off early," said Tony McNeil, an Interior Department laborer, checking his wristwatch. "If we were going to get off early, we should have been gone."

Many federal workers expressed cynicism about this year's appropriation brouhaha -- which ended with Reagan's signing the measure late yesterday afternoon -- and some expressed irritation about the politicians who control their budgets.

"Why do they get to wait until the eleventh hour?" said Linda Corbin, a Justice Department paralegal. "Why does this have to happen every year?"

Andrew A. Feinstein, who studies government shutdowns as staff director of the House civil service subcommittee, said the skepticism is understandable. "The general view of career civil servants toward this is sort of 'Ho-hum, we have to go through this again,' " Feinstein said. "They think, 'Why don't the politicians let us do our jobs?' "

Although the first such federal agency closing, a one-day affair in November 1981, caused widespread fear and anxiety, "what looked frightening then is routine now," Feinstein said.

One reason may be that a government shutdown is hardly a shutdown.

A poll of federal government agencies late last year by Feinstein's subcommittee, chaired by Rep. Patricia Schroeder (D-Colo.), showed that only 22 percent of federal employes are let off in these short-term furloughs.

Each agency must identify "essential" employes, who must keep working when the government is without appropriated funds.

Among them are U.S. Park Police and Border Patrol officers, air traffic controllers and all of the Defense Department's approximately 1 million employes. Veterans Adminstration doctors and nurses stay on, as do Social Security employes. Only 4 percent of Energy Department employes may walk.

But some agencies such as NASA, the General Services Administration, the Environmental Protection Agency and the Education Department ask more than 95 percent to leave.

Schroeder estimated that because Congress always has agreed later to pay the departing employes for work not done -- and never recovers the administrative expense of ushering them out -- a one-day government shutdown costs the taxpayers $55 million.