The nation's top military leaders in a report that rebuts charges by the former head of Air Force Intelligence, yesterday disputed the claim that the United States has lost its strategic edge to the Soviet Union.

"The Joint Chiefs of Staff," consisting of the heads of the military services, "do not agree that the Soviet Union has achieved military superiority over the United States," Air Force Gen. George S. Brown, chairman of the joint chiefs, said in the report released yesterday by Sen. William Proxmire (D.-Wis.)

In their 11-page paper, the chiefs took direct issue with Air Force Maj. Gen. George J. Keegan Jr., who said in farewell remarks as he retired as head of Air Force Intelligence on Jan. 1 that the Soviets had gained superiority over the United States.

"I am unaware of a single important category" involving the strategic balance "in which the Soviets have not established a significant lead over the United States," Keegan said in a New York Times interview published Jan. 3.

While agreeing with Keegan that Soviet longrange missiles can lift heavier nuclear warheads with more explosive power than their American counterparts, Brown, speaking for the chiefs, said that "the United States has a substantial lead over the Soviet Union in bomber payload, missile accuracy, survivability and numbers of warheads and bombers."

"The available evidence," Brown continued, "suggests the U.S.S.R. is engaged in a program to achieve" military superiority over the United States "but that they have not attained this goal."

These and other statements by the Joint Chiefs of Staff are expected to be discussed today if the Senate Defense Appropriations Subcommittee meets as scheduled to hear testimony from Gen. brown and Defense Secretary Harold Brown.

"The United States is moving in the correct direction" both militarily and diplomatically in regard to the Soviet Union, the chiefs said in a statement that indicates military and civilian leaders agree on overall strategy.

Keegan has been warning about the Soviet threat through most of his Air Force career, and helped make an independent assessment of Russian military programs for the director of the Central Intelligence Agency. He did this as a member of the panel known as "Team B," which worked independently to produce a report separate from the national intelligence estimates put together by the CIA.

In discussing 25 separate issues of American strategic policy, the chiefs did provide ammunition for those warning that the Soviet civil defense Program should be viewed with grave concern.

Brown, on behalf of the chiefs, disputed Keegan by declaring in the report that despite Soviet civil defense efforts, U.S. weapons "through the 1980s" would be able to inflict the amount of retaliation on Russia that national policy makers want.

Secretary Brown told the Senate Armed Services Committee last week that U.S. nuclear weapons could overcome Soviet defenses in a nuclear war. Other arms specialists have argued that living underground eventually would prove futile because lethal radioactivity would last longer than food stored in shelters.

The chiefs, in their report, said the Soviet civil defense program is "more extensive and better developed than it appeared to be several years ago."

"Under optimum conditions," which include a warning prior to U.S. attack and successful evacuation and other preparations, Soviet civil defense measures could probably "lessen damage and protect the Soviet leadership and most of the city population," the report said.

The chiefs also conceded that "civil defense has received little consideration during past U.S.-Soviet arms control negotiations." Keegan has charged that the 1972 treaty limiting missile defenses by both sides was based on the wrong assumption that the Soviets were not seriously building a defense for nuclear war.

The chiefs confirmed that "some current studies indicate" that 10 times as many Americans as Russians might be killed in a nuclear exchange "but only in a worst case scenario . . . such studies are scenario-dependent and should not be regarded as definitive forecasts of outcomes."

Proxmire, in releasing the report of the joint chiefs yesterday, said: "This was a courageous statement by the Joint Chiefs of Staff" who "publicly refute" the "exaggerated and, in many cases, erroneous claims of Gen. Keegan."

Proxmire, who in te past has often assailed military and civilian leaders at the Pentagon, called the chiefs' statement "a service to the American public which needs a fair accounting of Soviet activities, not scare tactics."