The United States has given South Korea more than twice as much aid in the past four years as the People's Republic of China and the Soviet Union combined have given to North Korea in that time, two congressmen said yesterday.

Reps. Thomas J. Downey (D.-N.Y.) and M. Robert Carr (D-Mich.), members of the House Armed Services Committe, said South Korea has received enough aid from this country that it should be able to defend itself if U.S. ground troops are withdrawn, as President has proposed.

"If, after all we have given it and all President Carter plans to give it, the South Korean government is unable to defend itself, this will be the South Korean government's fault and not ours," the two said in a press release.

South Korea received $770.4 million in various forms of military aid from the United States during fiscal years 1974 through 1977. According to Defense Department figures declassified Friday at Downey's and Carr's request, North Korea received of $180 million from the Chinese and $145 million from the Soviets during the same period.

If only the two most recent years are totaled, the congressmen said, South Korea has received 3.1 times as much military aid from its most powerful ally as North Korea has gotten from its two principal suppliers.

"These figures destroy the image of North Korea as a muscular giant about to swallow up the helpless South the moment we pull out," said the joint statement.

"The South has twice the population and more than three times the gross national product of the North. If, under these circumstances, some say the South is unable to defend itself without U.S. firepower, we are entitled to ask why."

Carter's proposal to withdraw the roughly 33,000 - American ground troops in South Korea has been shrouded in controversy since the former chief of staff of the U.S. command there, Maj. Gen. John K. Singlaub, predicted shortly after the move was announced that it would "lead to war."

After Singlaub was transferred, and the fallout from his statement had dissipated somewhat, Army Chief of Staff Bernard W. Rogers revealed to a House committee that the Joint Chiefs of Staff had recommended a much smaller withdrawal than Carter had proposed.

The chairman of the joint chiefs, Gen. George Brown, acknowledged in testimony the next day that Carter's plan differed "in a fundamental way" from that of the chiefs, but that the military leaders considered it "an acceptable risk."

Later, a Pentagon task force concluded that South Korea might need as much as $8 billion in additional military equipment - in addition to the U.S. air and navel forces Carter pledged to leave in the area - to offset the withdrawal.

Carter and the Pentagon still advocate the withdrawal, which might explain the timing of the declassification of the figures on aid North Korea has received from the Communist superpowers.

Several lawmakers, however, including Rep. Samuel Stratton (D.-N.Y.), chairman of a powerful House Armed Services subcommittee, have indicated that they think the withdrawal may be military unwise.

Complicating matters further is the ongoing probe of alleged South Korean influence-buying in the House, which administration officials fear may make legislators reluctant to vote for the additional military aid that will be requested for South Korea.