The House dealt President Reagan an astonishing spending defeat yesterday as it voted, 301 to 117, to override his veto of a $14.1 billion supplemental appropriations bill.

The Senate will take up the veto today, and Majority Leader Howard H. Baker Jr. (R-Tenn.) said the outcome is uncertain.

With two-thirds required to override, House Democratic leaders had 22 votes to spare as they racked up their biggest victory so far against a president who had defeated them at nearly every turn for the last year and a half.

It was the first time the House has voted to override Reagan on a money bill. The two chambers of Congress have overridden a Reagan veto only once, on a relatively minor copyright protection bill.

The Democrats held their own ranks, losing only 13 of their 233 voting members. With the help of moderate Republicans such as Rep. Silvio O. Conte (R-Mass.), ranking minority member on the House Appropriations Committee, they also picked up 81 of 195 GOP votes in a split similar to the one they suffered on the tax increase bill last month.

All Washington area House members, including Republicans, voted to override.

The veto battle, which many Democrats as well as Republicans had expected the president to win, came as an opening shot in a month of expected turmoil over spending before Congress quits for the Nov. 2 elections.

In action earlier in the day on spending for next year the House Appropriations Committee voted to keep the current pay ceiling for high-level government officials as well as members of Congress.

Its action would freeze annual congressional pay at $60,662.50 and keep the administrative pay cap at $57,500 a year. Congressional sources said this would have the effect of freezing salaries for about 24,000 government officials, even if the president and Congress, as expected, approve a 4 percent cost-of-living increase for other government workers next year.

The Democratic veto victory in the House came despite last-minute assurances from Reagan, in a telephone call to House Minority Leader Robert H. Michel (R-Ill.), that he planned to continue a popular jobs program for the elderly even though he had cited its funding, at $210.6 million, as a major reason for vetoing the bill.

Both Democratic and Republican leaders said the jobs program was a major factor in the outcome, along with other social programs that Reagan would have cut only two months before congressional elections.

Another reason for the Reagan rebuff, they said, was reluctance on the part of members of both parties to flip-flop on the measure, which had passed the House by an overwhelming bipartisan vote less than a month ago.

A third, they added, was the fact that, despite Reagan's claims that it was a "budget-buster," the bill actually would spend less than Reagan requested, especially for defense.

"It was not a good, solid position to defend. . . . The president's position is not very defensible when every member gets up and says we're a billion and a half under the budget," Michel told reporters after the vote.

The House was telling the president that "we've got a little bit different priorities," he added.

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) hammered at those very themes in an impassioned speech to the House just before the vote.

Appealing directly to the 130 Republicans who voted for the bill last month, O'Neill said it was they who would decide the fate of the measure, which he described as the product of bipartisan legislating.

"By vetoing this measure the president wants us to make a choice between weapons and handicapped children. Well, we do not have to accept this. We have made our choices. . . . Let's stick by them," he said. "Let's get America moving again," he added, "and let's not leave the elderly, the handicapped and the disadvantaged behind."

The bill included $918 million more than Reagan wanted for a variety of social welfare programs, especially for the elderly and for low-income students. It also included only $500 million of the $2.6 billion that Reagan requested for defense, along with $350 million for economic aid to Caribbean Basin and Central American countries.

In all, it was $1.5 billion less than Reagan had proposed in his request for supplemental appropriations to meet government payrolls and continue program operations through the end of the 1982 fiscal year on Sept. 30.

Some action on the bill is needed urgently because the Pentagon and many other departments and agencies are expected to be without funds to meet payrolls after the middle of next week.

If the Republican-controlled Senate follows the House and overrides the veto, the bill will take effect without Reagan's signature, assuring that the payrolls will be met next week. If it sustains the veto, Congress will have to scramble to come up with a compromise that meets Reagan's approval.

"Well, the big spenders won," Reagan said as he left Air Force One in Utah. He expressed the hope that his veto would be sustained by the Senate today, but White House deputy press secretary Larry Speakes conceded that Sen. Baker thought the vote would be close.

Appearing subdued, Reagan said his reaction was "one of disappointment."

"I can't say I was totally surprised," he said in response to a question. "We knew it was an uphill fight."

The reactions of several people in his entourage indicated that they were surprised, however. "I believe we were just a little bit overconfident," said Ed Rollins, the White House political director.

Although Democratic as well as Republican leaders were anticipating a Reagan victory in the House as late as yesterday, Democrats and some GOP critics of the veto capitalized on the popularity of the jobs program for the elderly, while Republican leaders tried in vain to head off a revolt with assurances that the program would be continued regardless of the outcome of the veto fight.

"We got the momentum today," said House Majority Leader James C. Wright Jr. (D-Tex.), as members began to question whether the program, under which about 54,000 retired people work at community service jobs in health, nutrition and other fields, would be continued. Documents reflecting the administration's qualms about the program were circulated widely.

The issue, said House Minority Whip Trent Lott (R-Miss.), was "devastating" and cleverly handled by the Democrats. Lott said both the administration and House Republicans could be faulted for their handling of the issue, but he said Reagan could not be blamed for vetoing the measure in the first place.

"You can't pick and choose your fights; you have to fight everyone," said Lott, adding that he hopes Reagan will continue to veto money bills that violate his own budget targets.

Although yesterday's vote was not related to upcoming fights over spending for fiscal 1983, which starts Oct. 1, the size of the House vote is expected to strengthen the hand of Democrats and moderate Republicans in resisting Reagan's expected attempts to squeeze domestic spending and increase Pentagon outlays.