President Reagan's budget request for defense could be reduced safely by $32 billion this year to bring an $11.1 billion cut in actual spending, the author of major Pentagon policy papers through Democratic and Republican administrations said yesterday.

William W. Kaufmann, a high-level consultant to defense secretaries from Robert S. McNamara to Harold Brown over the last two decades, makes that argument in the new study, "Setting National Priorities," published by the Brookings Institution.

Kaufmann's detailed recommendations pass fresh ammunition to those in Congress already taking shots at Reagan's request for a peacetime record of $258 billion for defense in fiscal 1983. The Senate is expected to take the first of several congressional votes on that request next week.

Kaufmann said he favors spending more than in the past to strengthen the nation's defenses but contended at a press luncheon at Brookings that the Reagan administration has gone overboard in its money requests.

Rather than go along with Reagan's request for annual spending increases of 8 percent for defense for the next five years, Kaufmann said, the nation would be better served by limiting the yearly increases to 6.5 percent and getting more bang for its bucks.

The new administration, he contended, has approved a Navy building program that would make the fleet top-heavy with nuclear-powered aircraft carriers and Aegis cruisers. The Pentagon estimates that its newest Nimitz carriers will cost $3.4 billion each and the Aegis $1 billion each.

If the Navy's idea is to go after Soviet ships in their home ports in a war rather than rely on submarines and land-based aircraft to hit them in narrow waterways, Kaufmann said, even the coveted 600-ship fleet would not be big enough.

A better idea would be to structure the future Navy to control the sea lanes and to carry troops and gear to distant trouble spots in a hurry, he said. This would require redirecting money from carriers and cruisers to destroyers, amphibious ships and high-speed cargo vessels, he said.

Kaufmann, political science professor at Massachusetts Institute of Technology and author of eight of the annual Pentagon posture statements on what the nation's military needs and why, also would chop Reagan's proposed 8 percent pay raise for fiscal 1983 to 6.5 percent.

He also recommended canceling construction of the B1 bomber, calling it "a lovely plane whose time has come and gone," and building fast cargo ships rather than buying a new fleet of Lockheed C5 transport planes.

When a war starts, he said, planes, no matter how large, can deliver only "penny packets" of stuff. High-speed ships racing to Europe under Navy convoy would be needed to feed any modern army, he said at the news conference.

In his chapter titled "Setting National Priorities," Kaufmann made these other points:

* If the administration really believed the nation faced a military crisis, it could resume draft calls and put more bombers and submarines on patrol.

Because no such emergency measures are contemplated, "there is much to be said for slowing, deferring or even canceling certain programs until specific threats, missions, equipment and forces have undergone a systematic assessment."

* To make sure that at least some U.S. forces are ready for immediate action, some units should be exempted from budget cuts. Better to have 30 percent of the forces ready for action "than an effectiveness of 80 percent across the entire force."

* Since the Trident 2 missile to be deployed on submarines can destroy Soviet missile silos "almost as effectively as the MX and with much shorter flight time," there is no need to rush a plan to house MX missiles temporarily in Minuteman silos, as the administration proposes.

* Expanding the U.S. civil defense program would buy little real protection. The same is true of spending billions on fighter planes to defend the continental United States against Soviet bombers when the major threat is from missiles, against which the United States has mounted no defense.

* Neither the United States nor the Soviet Union has figured out how to fight a land war in Europe with tactical nuclear weapons "in any organized and systematic way . . . .Their use on a battlefield, even on a limited scale, is likely to eventuate not only in terror and total demoralization among all the participants, but also in a rapid escalation of the local conflict."

* Adding Pershing 2 and ground-launched cruise missiles to the U.S. tactical nuclear arsenal in Europe, as proposed, would add "yet another layer to what is fast becoming the main archaeological dig of the nuclear age."