The Reagan administration's request for production of 21 more MX nuclear-warhead missiles yesterday passed its final hurdle when the House bowed, 217 to 210, to the will of the president.

Attention immediately shifted to President Reagan's fiscal 1986 request for 48 additional missiles, with MX opponents and supporters predicting it will be scaled back sharply, if not eliminated, as part of deficit-reduction efforts.

The MX survived four votes over the last two weeks, two each in the House and the Senate. The votes were on releasing MX production funds for the current fiscal year.

Yesterday's House outcome, following a similar 219 to 213 vote on Tuesday, was expected even by MX opponents, who found themselves unable to overcome Reagan's arguments that U.S. arms control negotiators in Geneva needed the affirmative MX vote. The negotiations began this month.

"All I know is that in Geneva today they can sit down at the negotiating table and know that we came forward in a bipartisan manner and have voted for this weapons system," the president told told reporters in New York.

The vote increases the number of authorized missiles to 42, the others being authorized in fiscal 1984. Ten of the missiles have been built and are scheduled to be deployed in silos in Wyoming in late 1986.

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and other MX opponents had promised an "all-out" effort to kill the missile in yesterday's voting, but there were few changes between the two House ballots this week. As on Tuesday, 61 Democrats yesterday voted with Reagan. Twenty-three Republicans voted against him, one fewer than in the first vote.

There were no switches, despite heavy lobbying Wednesday by the administration and anti-MX groups. But two Democrats and three Republicans did not show up this time, including Rep. Mervyn M. Dymally (D-Calif.), who opposed the MX on Tuesday.

Dymally's aides said he was in the "Caribbean . . . on business," but Democratic sources said Dymally had been under pressure not to oppose the MX because 5,000 jobs in his Los Angeles district are dependent on Northrop Corp., an MX contractor. "He was the only walker," said one Democratic official, describing the tendency of some lawmakers to avoid a tough vote by "taking a walk."

The other absentees were Rep. Thomas J. Ridge (R-Pa.) and Rep. John Conyers Jr. (D-Mich.), both of whom voted against the MX on Tuesday, and Rep. Philip J. Crane (R-Ill.) and Rep. Bill Archer (R-Tex.), who supported it. Aides for all four said they missed the vote because they had been in places where vote warning bells had not sounded.

The Democratic leadership was noticeably less aggressive yesterday in lobbying members than in previous MX votes, Democrats said. Lawmakers said this reflected an ambivalence in the leadership toward winning a vote that many Democrats felt would only add to the impression that the party was "soft" on defense.

"I don't think they wanted the consequences of winning it," said one Republican official.

One of those the leadership did work on yesterday was Rep. Harold E. Ford (D-Tenn.), who had opposed the MX on Tuesday but had told Democratic leaders that he would change his position after pressure from the White House and Democratic supporters of the MX.

Yesterday, Ford was the last person to vote. After what several Democrats said was a sharp anti-MX lecture from Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.), Ford, who serves on Ways and Means, stood in the front of the House chamber with a green "yes" card and a red "no" card. After several minutes Ford voted with the Democratic leadership and opposed the MX.

The vote yesterday occurred after two days of debate on the missile in which many lawmakers from both sides of the aisle made it clear that they were supporting the weapon this time because of its connection with the arms control talks but that they are unlikely to give such support to future MX funding or to the Reagan defense buildup in general.

Rep. Norman D. Dicks (D-Wash.), one of a group of Democrats who helped the administration win MX votes, said yesterday that the administration "is down to the end of the road" on the MX. Dicks said he might support a proposal to "zero out" all the MX money from the fiscal 1986 budget request.

Rep. Nicholas Mavroules (D-Mass.), a leading MX foe, predicted that yesterday's vote to release $1.5 billion to build the 21 missiles would be "the last positive vote for the MX."

As a sign of the problems Reagan now faces, four Democratic senators who consistently have supported the MX, including Sam Nunn (D-Ga.) and Minority Leader Robert C. Byrd (D-W.Va.), yesterday proposed capping MX deployment at 40 missiles rather than the 100 missiles Reagan seeks. They said they also would cut the fiscal 1986 request to 12 missiles and restrict them to testing.

MX opponents in the last few days focused on the MX's impact on the deficit, arguing that to build the missiles and harden their silos to withstand a Soviet attack would cost $43 billion.

"The closeness of the vote, given the extremes to which Reagan went . . . indicates very strongly . . . that Congress is no longer in a mood to sign a blank check for Pentagon wish lists," Majority Leader James C. Wright Jr. (D-Tex.) said.

"The hawks are for giving them the rate of inflation and the doves are for not giving them the inflation rate ," House Armed Services Committee Chairman Les Aspin (D-Wis.) said.

Aspin said he thinks that the defense budget should grow 3 to 5 percent after inflation for "national security" reasons but said he would support a freeze on defense if it were part of an overall freeze.

House Budget Committee Chairman William H. Gray III (D-Pa.) said Reagan's hard sell on the MX may return to haunt the administration on its defense budget request. "I think winning here is going to hurt him. He got his bargaining chip here," Gray said.

"I do still believe that a key factor in this vote was the ongoing talks in Geneva," said House Assistant Minority Leader Trent Lott (R-Miss.), who also credited Aspin with helping to develop a consensus with House Democrats on the missile.