An attempt by Senate Minority Leader Howard H. Baker Jr.(R.-Tenn.) to alter the strategic arms limitation treaty substantially failed by a single vote in the Senate Foreign Relations Committee yesterday.

Three Democrats joined Baker and three other Republicans to vote for the proposal, which Baker said yesterday had only symbolic significance, and which he had described last June as "a movement in the wrong direction."

Treaty supporters said the Baker amendment would effectively kill SALT II. A combination of six Democrats and two Republicans voted to defeat it.

Also yesterday, Majority Leader Robert C. Byrd (D-W. Va.) threatened to bring SALT II up on the floor before the Senate considers the "windfall profits" tax on oil companies, a move that would disrupt the Senate's schedule but perhaps improve the chances of a vote on SALT II this year.

Baker's proposal was to permit the United States to build and deploy 308 "heavy" land-based intercontinental ballistic missiles to match the Soviets in this category. Baker admitted, however, that the United States does not want this type of weapon and would not build it even if permitted to do so by the treaty.

Last June, when Baker first announced that he was opposing SALT II as written because of his concern over heavy missiles, among other issues, he was asked if he would favor the sort of amendment he proposed yesterday. Baker replied that he would not, that such an amendment would be a "movement in the wrong direction" because it would further the arms race, not reduce superpower arsenals.

Yesterday Baker said he still preferred eliminating the Soviet Union's heavy missiles, but would favor the approach of his proposal as better than nothing.

The Soviets' 308 heavy missiles are much bigger than anything the United States has ever built or even contemplated. The first Salt agreement on offensive arms and then Salt II permit the Soviets to maintain these rockets, the heart of the Soviet Union's land-based force, while prohibiting the United States from acquiring them.

The Nixon, Ford and Carter administrations justified this exception for the Soviets' heavy missiles as simply a reflection of the status quo for which the United States is compensated in other provisions of the SALT agreements. But Baker said yesterday that the exception was a one-sided provision that contradicted the Senate's instructions, given when SALT I was approved, that SALT II should give the United States strategic nuclear forces that are "not inferior" to those of the Soviet Union.

Baker said he was sure that a firmer negotiating position would have persuaded the Soviets to give up some or all of the SS9 and SS18 rockets, which are the most formidable weapons in their arsenal.

Presidential counsel Lloyd N. Cutler, speaking for the administration, said that Baker's proposal, if adopted, would lead to reopening the SALT negotiations and would require the United States to make concessions to the Soviets. This, said Cutler, was too high a price to pay for a change in the treaty that Baker acknowledged was only symbolic.

Last week, the chairman of Baker's undeclared presidential campaign, Sen. Richard G. Lugar (R-Ind.), warned the Foreign Relations Committee against approving "cosmetic" changes in SALT II, then claiming that it had taken a tough position. Cutler picked up Lugar's language yesterday, saying of Baker's heavy missile proposal: "If there ever was a cosmetic amendment, this is it."

The three Democrats who voted for Baker's proposal were John Glenn (Ohio), Richard Stone (Fla.) and Edward Zorinsky (Neb.).

Byrd suggested the possibility of considering SALT before the "windfall profits" tax at a breakfast for congressional leaders at the White House yesterday. Byrd has been trying, without success so far, to get unanimous consent for a time agreement that would limit the SALT debate.

Senate leaders apparently hope that the threat of losing their long Christmas and New Year's recess will be enough to get action on SALT this year, but that schedule remains problematical.