The Senate voted yesterday to retain federal control over National and Dulles International airports, an action that may threaten a Reagan administration proposal to sell the federally owned airports to a regional authority.

The Senate approved an amendment to lease the airports for 50 years by a voice vote amid signs that proponents of the sale were on the defensive. The leasing measure differs sharply from the sales measure supported by the administration.

The administration plan calls for control of the two airports to be placed in the hands of the regional authority after a 35-year lease. Under the Senate measure adopted yesterday, a transportation secretary could negotiate a sale of the airports, but Congress must approve the sale.

The amendment was offered by Sen. Paul S. Trible (R-Va.) in the face of mounting opposition over the $47 million sales price for the two airports. Trible's amendment came on the heels of a close vote on an amendment by Sen. Ernest F. Hollings (D-S.C.) to raise the price from $47 million to a minimum of $111 million. That effort lost by only two votes.

Trible's surprise move also followed a speech by Sen. Barry Goldwater (R-Ariz.), in which he blasted the sales price. "I think it's absolutely stupid," said Goldwater. "It doesn't make common sense to give something like this away."

Trible said last night the amendment providing for continued federal control "renders moot the concerns about price" held by other senators. "Few senators had a quarrel about turning over these airports for airport purposes," he said. "Their concern was that the price might not be fair."

"I don't really care who owns the airports . . . . The purpose is to . . . free [them] from the shackles of the federal government," he said, adding that the 50-year lease would do that.

"I believe we have the votes to prevail," he said.

Sen. Paul S. Sarbanes (D-Md.), leader of the opposition to the bill, said it is unacceptable in its amended form and he hopes to defeat it.

A final vote is expected today.

The transfer bill is considered crucial to both airports because the federal government has been unwilling to spend the millions of dollars that local officials say are needed to accommodate either the growth at Dulles or the congestion and outdated buildings at National.

Maryland officials fear that new facilities at Dulles and National will hurt the efforts of Baltimore-Washington International Airport to grow.

Maryland officials have argued that because National and Dulles were built with federal dollars, the two Virginia airports have an unfair advantage over the Maryland airport. To allay the fears of senators sympathetic to Maryland's argument, the bill was changed in committee to require the airport authority to pay Maryland $36 million.

Even if the bill is approved by the Senate, it faces a tough fight in the House.