Military buses pulled up at the Capitol yesterday and ferried more than 100 House members to the White House for a last-minute plea from President Reagan and his chief arms negotiator to support the MX missile when the House votes today.

Reagan also telephoned key lawmakers. Negotiator Max M. Kampelman, who flew in from the Geneva arms talks this weekend, spent the day shuttling between Capitol Hill and the White House, as the administration went all out to add another MX victory to the one it secured in the Senate last week.

In a strongly worded appeal delivered with the president at his side, Kampelman told the lawmakers that a defeat for the MX would make a concession to the Soviets "without the necessity for them to give something in return."

"As they enjoy the apple that falls from the tree that they did not have to pay for, they quite understandably wonder what other fruit may fall from that tree that they do not have to pay for," he said.

Kampelman, a Democrat, warned the House members that defeat of the MX would "inevitably delay the negotiations" in Geneva.

As the sharply divided House began debate on the MX yesterday, leaders of the Democratic-controlled House said the vote was too close to call, but there was growing concern yesterday among anti-MX lawmakers as White House lobbying intensified. In addition to Reagan, Vice President Bush, Secretary of State George P. Shultz, Defense Secretary Caspar W. Weinberger and former president Gerald R. Ford have been contacting lawmakers.

About 25 members were on the fence when yesterday's lobbying began. And vote counters on both sides said those members held the outcome in their hands.

MX opponents conceded that they had an "uphill" fight to defeat the nuclear weapon in the face of the recently resumed arms talks, Reagan's strong push and his comfortable MX victory in the Republican-led Senate last week. Congress has never denied a president a major strategic weapon system.

"It's very, very close," said House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.), who, like the rest of the Democratic leadership, is opposed to the MX. "I'm sure the White House appreciates that it's close or they wouldn't be turning out all the stops they are."

Anti-MX groups were doing their share of lobbying yesterday to counter the administration's blitz, collaring undecided or wavering lawmakers in the corridor outside the House chamber.

"I think they're not just trying to win, but are trying to win big to establish momentum for other votes" on other tough issues, said one House Democratic official involved in the MX fight. "They would not be investing the president's prestige unless they thought they were going to enhance it."

The issue scheduled for a vote today is whether to release $1.5 billion frozen by Congress after narrow votes last year for 21 additional MX missiles. The Senate, in two identical 55-to-45 votes, agreed to release the funds. The House will vote twice also, and the administration must win both votes to have the money released.

Reagan, who calls the MX the "Peacekeeper," said yesterday it is needed to force the Soviets to negotiate arms reductions. He recalled that Moscow bargained on the ABM treaty only after Congress voted to build an antiballistic missile system.

Reagan said the United States had asked its European allies to "walk through fire" to deploy medium-range missiles and that a defeat for the MX now would be a signal that this country is "irresolute and divided."

A vote to kill the missiles would "send a message to the Soviet Union that as far as the House of Representatives is concerned we were willing to give away this missile . . . without getting a single concession . . . ," Rep. Samuel S. Stratton (D-N.Y.) said during yesterday's debate. He added that killing the MX could cost 32,000 jobs.

MX opponents charged that the 10-warhead missile is too costly -- they estimate it could cost $43 billion more -- and too vulnerable because the missiles are to be placed in old Minuteman silos that the Soviets can easily locate.

In addition, opponents said that they think that canceling the missile would have little affect on the arms talks, since the Soviets have made it clear they are more concerned about Reagan's space-based weapons program.

"This argument has come down to if you're not supporting the MX, you're not patriotic and if you're a Democrat, you're weak on defense ," said freshman Rep. James A. Traficant Jr. (D-Ohio). "Well, I don't agree with that. This MX is a sitting duck."

The budget argument against the MX apparently has hit home with many lawmakers. Rep. Richard A. Gephardt (D-Mo.), who is helping lead the effort to defeat the MX, said yesterday, "I really think the budget-deficit issue is really starting to impinge on this thing. You're talking another $25 billion to get the missile and another $15 billion to harden the silos to make them less vulnerable , and it doesn't get you anything."

But MX supporters said the overriding issue in the vote appears to be concern about harming the Geneva arms talks. "Without the arms control talks resuming I don't know whether we could've won it or not," said House GOP Minority Whip Trent Lott (R-Miss.).

That was the point Reagan and administration officials pressed in their lobbying yesterday. The focus was on about a dozen wavering or undecided Democrats and another 10 Republicans, but even the committed got telephone calls.

Gephardt, Majority Leader James C. Wright Jr. (D-Tex.) and Majority Whip Thomas S. Foley (D-Wash.) were among those called by Reagan. According to officials, Reagan in some of his calls mentioned Sunday's shooting death in East Germany of an U.S. military officer by a Soviet soldier before asking for support for the MX.

Also yesterday, Reagan told a breakfast meeting of reporters that he has asked a Republican campaign committee to cancel a $5 million negative campaign against Democratic House members. The campaign had apparently complicated White House lobbying efforts for the MX. Reagan said he had told Rep. Guy Vander Jagt (R-Mich.), chairman of the National Republican Congressional Committee, of "my desire that we stop this and go forward with those areas where partisanship should stop, particularly at the edge of the water."

Kampelman met early in the day with O'Neill and then held a series of meetings.

The administration's decision to fly Kampelman to Washington on the eve of the House vote drew some barbs yesterday.

"I think it's an error for the ambassador to be used to lobby the Congress," said Sen. Claiborne Pell (D-R.I.).