House Democratic leaders kept party liberals and conservatives together yesterday to beat back Republican efforts to cut the fiscal 1980 budget.

The key vote was a 198-to-218 defeat of an amendment by Reps. Marjorie Holt (R-Md.) and Ralph Regula (R-Ohio), which would have reached the fiscal 1980 deficit to $18.7 billion, while offering a tax cut of $15 billion.

Earlier, the House had defeated an amendment by Rep. Delbert Latta (R-Ohio), which would have cut the deficit to $15.2 billion.

The votes came as the House continued work on the preliminary resolution for next year's budget.

Democratic leaders worked hard to defeat the Holt-Regula proposal, which they feared might pass in this year of austerity.

House Speaker Thomas P. (Tip) O'Neill Jr. sent a letter to Democrats urging them to defeat the Holt-Regula amendment because it would "emasculate traditional Democratic programs" and injure the economy.

Majority Leader Jim Wright (D-Tex.) in a floor speech said the programs that would be affected ranged from federally aided highways to Head Start, from sewage treatment plants to low rent housing and urban mass transit.

Wright called the amendment "almost seductive in its sweet alure" of a tax cut plus a lower deficit, but added it would cut deeply into many programs and be "a veritable who's who of who does not count." He said the cuts would take "the heart and soul and life blood" out of the programs.

Holt said her amendment would deep, saying they were only about 1 percent in each function and she denied that anyone could say specifically what programs would fall. She said the proposal increased spending for defense by $1 billion and health by $787 million.

Hold said her amendment would put us within striking distance of a balanced budget" and was "simply limiting growth of government."

While Holt-Regula was the most attractive Republican amendment, it was not the official Republican budget cut amendment.

That was offered by Latta. It would have set outlays at $523.4 billion, as opposed to the Budget Committee's $538.7 billion, and a deficit of $15.2 billion with a net tax cut of $6.5 billion.

Housing Minority Leader John Rhodes (R-Ariz.) said the Republican substitute would send a "signal to the rest of the people of the world that the United States is very serious about taking control again of our economic destinies."

Also defeated, 371 to 45, was an amendment by Rep. John Burton (D-Calif.) that would have balanced the budget by taking away from the Pentagon and the Department of Energy authority to spend some $22.4 billion in unobligated funds and by increasing revenues by $3 billion through repealing a foreign tax credit for oil.

An amendment to cut $650 million from the food stmp program was defeated 276 to 147. An amendment to restore 50 percent of state revenue sharing money was defeated 216 to 203.

The House, which has now spent seven days on the budget, will take it up again today. While passage of the resolution is not certain, defeat of the Holt-Regula amendment enhances changes that the Budget Committee's proposal will pass virtually intact.

The House Budget Committee, in recommending spending of $538.7 billion, suggested a deficit of $24.9 billion. The Senate, using different economic assumptions, approved a budget calling for a deficit of about $29 billion. President Carter's proposed budget would provide for a deficit of about $28 billion.