The natural gas compromise is expected to win its first test vote on the Senate floor today.

The Senate will vote on a motion to send the bill back to a House-Senate conference with instructions to Senate conferees to fight to strike pricing provisions from the measure.

If the motion is defeated, opponents would have eight more days to try to fashions a recommittal motion that would pass. If the motions fail, the Senate has agreed to vote next Wednesday on adoption of the conference report, which calls for an end to controls on prices of new gas by 1985.

Majority Leader Robert C. Byrd (D-W.Va.), predicted yesterday that the first recommittal motion, offered by Sen. Howard Metzenbaum (D-Ohio), would fail and would be supported by not more than 35 to 45 votes.

It appears as though a late but hard lobbying job by President Carter has given the gas compromise the momentum to push through the Senate. But Byrd and the bill's chief sponsor, Sen. Henry M. Jackson (D-Wash.), refused to claim the votes to pass the bill until they see the outcome of today's vote.

"We're in goon shape," said Jackson. "Let's see how the vote goes tomorrow. If they (opponents) are below 40 votes they're in trouble."

Normally, they should be in trouble if they're below 50 votes, which is half the Senate. But Jackson assumes that some opponents of the bill have been persuaded to vote against the motion to recommit as an unworthy way to kill it. He has argued that recommittal would kill the bill because, after eight months of labor to produce the compromise, House conferees won't negotiate anymore.

Metzenbaum said yesterday he was "not overly optimistic" about chances of winning today, but said eight additional days would give the bill's opponents time to try to put together a winning proposal.

The multibillion-dollar gas proposal, which supporters say will increase gas supplies and liberal opponents say will only increase price, is the only major part of Carter's top priority energy bill with any chance to pass this Congress. It bears little resemblance to his original proposal.

Carter wanted to continue price controls at higher levels. The house supported the plan but the Senate voted to end controls in two years after breaking a filibuster Metzenbaum and others had mounted against deregulation. The compromise is being opposed by a coalition of pro-producer senators who feel it doesn't deregulate quickly enough and pro-consumer members who oppose deregulation at any time.

Metzenbaum said that if the administration had "put 50 percent of the effort into last year's Senate fight that it did at Camp David (on the Mideast settlement), we wouldn't be in this situation today."