President Reagan, anticipating that Pentagon waste and fraud will become an issue in Sunday's campaign debate, yesterday launched a preemptive strike with a ceremony in the White House Rose Garden to honor Defense Department whistle blowers.

Describing a dozen Pentagon employes as the "unsung heroes of peace," Reagan said the administration's "hard work is paying off" and "we're tackling the tough problems that have plagued defense management for many years."

Reagan campaign sources said they expect Walter F. Mondale to bring up examples of Pentagon waste, including a $7,400 coffee-brewing machine for the C5A cargo plane, in Sunday's debate as a way to criticize the overall Reagan defense buildup.

The administration has been particularly sensitive about charges of waste and fraud in procurement since accounts of overpriced tools and spare parts began surfacing simultaneously with Reagan's push for a $1.5 trillion, five-year increase in defense spending.

Internal memos released this week show that Defense Department officials devised an election-season "public affairs plan" during the fall presidential campaign for "publicizing the accomplishments" of the Pentagon in fighting waste, fraud and abuse.

Yesterday, White House officials staged a briefing for reporters by Pentagon Inspector General Joseph H. Sherick on efforts to combat waste and fraud. Sherick said he had given the same briefing last week at the Pentagon. He said he didn't mind the election-year attention because it helped send a warning to the "crooks and dummies" who steal from, and mismanage, Defense programs, as well as to honest employes who inform on them.

"I live on whistle blowers," he said, presenting charts to show that the fight against waste and fraud had intensified since 1981. Sherick said the Defense Department hotline "gathered dust" during the Carter years but had been revitalized in the Reagan administration.

One well-known whistle blower not present yesterday was A. Ernest Fitzgerald, whom Pentagon officials tried to prevent from testifying before Congress last June about cost data; he later testified under subpoena.

Fitzgerald was fired from the Pentagon in 1969 after he disclosed to Congress large cost increases in contracts for the C5 cargo plane. He returned to the Air Force two years ago after he and the Air Force settled a lawsuit he filed.

Yesterday, Sherick said, among other things, the Pentagon auditors had found faulty B52 wing bolts, substandard metal for Navy ships and defective parachute cord. Deputy Defense Secretary William Howard Taft IV stressed that the inspector general "works for us" and said it is "a difficult, painful process for us" because "we wish there weren't as many problems as they're able to fix."