The Reagan administration, which has done everything but call Libyan strongman Muammar Qaddafi public enemy No. 1, notified Congress yesterday that it intends to allow an American firm to help hook him into an Arab communications satellite system.

The deal calls for Ford Aerospace to sell satellite parts to a French firm, Interspatiale, which is wiring Libya and 20 other African and Arab nations, plus the Palestine Liberation Organization, into an elaborate communications satellite system.

A State Department official said that although it is largely a commercial transaction, the communications system has enough military potential to require notification of Congress. It would take a vote of both the House and Senate to stop the transaction.

Chairman Charles H. Percy (R-Ill.) of the Senate Foreign Relations Committee said yesterday that he had already warned the State Department that "there might be serious objections" to the deal in Congress.

Sen. Joseph R. Biden Jr. (D-Del.) disclosed the administration's intention to approve the "Arabsat" deal during a committee hearing where Defense Secretary Caspar W. Weinberger was testifying on President Reagan's strategic arms program.

"Tens of millions of dollars" are involved, Biden told Weinberger, to help Libya, the People's Republic of Yemen and the PLO, among others, to gain a system with military potential. Weinberger said he would "have to know more about it" before commenting on the proposal.