President Reagan's finding in January that El Salvador's progress on human rights entitled the country to continued military aid was a "sham" unsupported by any research, the American Civil Liberties Union charged yesterday.

The ACLU said documents released under the Freedom of Information Act disclosed no research or analysis by any U.S. intelligence agency backing that finding.

Instead, the ACLU said, the documents show that the Reagan administration merely relied on unverified statements by the Salvadoran government and on Salvadoran press reports to certify, as required by Congress, that El Salvador was making a "concerted and significant effort to comply with internationally recognized human rights."

The ACLU also released letters asking the chairmen of the House Foreign Affairs and Senate Foreign Relations committees to require the administration to have intelligence agencies prepare an "independent assessment" of the human rights situation in El Salvador before making its next certification later this month.

A State Department official said yesterday Reagan would certify continued improvement by the July 28 deadline.

"The administration has not taken the process of certification seriously . . . and we have every reason to think that the same thing is going on now," said Morton Halperin, director of the ACLU's Center for National Security Studies.

"If the intelligence community was asked to do a study, it would do an honest, straightforward study, and I think that's the reason they have been asked not to do a study," Halperin said.

"It knows what everybody knows: namely that these conditions have not been met, were not met six months ago and will not be met now."

The Reagan administration has a "need not to know" the actual human rights situation in El Salvador in order to be able to certify improvement and continue sending aid there, Halperin charged.

"In order not to tell us what's going on, they're not going to find out what's going on, and didn't find out the last time, because they don't want to know," he said.

The United States sent $81 million in military aid to El Salvador this year and has asked Congress for $61.3 million in military aid for the next fiscal year, according to the State Department.

Halperin dismissed a State Department cable sent to the embassy in El Salvador outlining an ambitious program of human rights improvements the United States wants put into effect there.

The cable, Halperin said, "in effect tells them to produce information which can justify the certification."

Under a law passed by Congress last year, the president must certify twice yearly, as a condition for continuing military aid, that El Salvador is improving human rights, controlling its armed forces and making continued progress on land and other economic and political reform.

But the law merely requires the president to make that finding and contains no provision under which Congress can override his assessment.

Halperin urged Congress to cut off funds to El Salvador for the next fiscal year "on the basis of our finding that the certification conditions were not met." If funding isn't terminated, Halperin said, Congress ought to change the certification process and require the president to submit his report to Congress for its independent approval.

Halperin said the freedom-of-information request disclosed that no intelligence agencies--including the Defense Intelligence Agency and the State Department's bureau of intelligence and research--prepared any documents or did any research supporting certification.

The CIA has not yet responded to the request, but his sources there indicated that the agency also didn't participate, said Halperin, a former National Security Council member.

The ACLU released its own report on El Salvador before the January certification, charging the government there with responsibility for an estimated 12,501 murders during 1981 and detailing charges of torture, arbitrary arrests and denial of rights. The group said it will release an updated report later this month.