Chairman Joseph P. Addabbo (D-N.Y.) of the House defense appropriations subcommittee said yesterday that he will try to cut $15 billion from President Reagan's new defense budget and predicted that it would be "easy" to get congressional agreement for at least a $10 billion reduction.

"Right now, the attitude of the people in Congress is that the defense department is not sacrosanct," Addabbo told reporters in explaining his optimism about achieving deep cuts in Reagan's request for $257 billion for defense in fiscal 1983.

Addabbo acknowledged that a $15 billion cut in budget authority would translate into about a $4 billion reduction in spending. This is because the money Congress approves in one year is spent over several years.

Even so, Addabbo contended after an all-day subcommittee hearing, it is important to show the public that the Pentagon is sharing in cuts of government programs. Until now, Addabbo complained, budget slashing has almost exclusively involved domestic programs, ranging from federal health care to college loans.

"I'm getting a little stronger vibes" this year than last about the need for cutting defense as well, Addabbo said in relaying the sense of his congressional colleagues.

"I figure $10 billion would be easy," he said in predicting how large a reduction Congress would approve. "Hopefully, we'll do better than that. I think we can," he said, setting $15 billion as his new target.

Addabbo, whose subcommittee recommends to the House how much should be approved for specific Pentagon projects, said he would start by trying to sink the two nuclear-powered aircraft carriers requested in the new defense budget. If both cannot be deleted, Addabbo continued, he will settle for one.

"I still believe the military put this budget together," he said in dismissing the Pentagon's request as the wish list of generals and admirals rather than a well-reasoned program.

Addabbo lashed out at the proposed budget after hearing Defense Secretary Caspar W. Weinberger and Gen. David C. Jones, chairman of the Joint Chiefs of Staff, testify that the budget is a realistic statement of needs for rearming the United States to cope with the Soviet threat.

"You would do an enormous amount of damage," Weinberger warned the subcommittee, if Congress tried to ease the government deficits by reducing Pentagon spending by $10 billion. He said every $1 cut from spending would mean taking $4 out of budget authority.

Obtaining immediate spending reductions would require slashing accounts that keep the military ready to fight--such as forward deployment of ships, flying hours and training exercises, Weinberger said.

Although such superweapons as the MX missile, B1 bomber and Navy ships will cost hundreds of billions of dollars, Weinberger said, canceling them this year would not shave much off Pentagon spending because money dealt with by Congress in budget authority accounts are only down payments on these weapons.

Weinberger said the domestic and defense budgets should not be viewed in the same way. The Soviet threat is real and growing and must be met with higher defense spending for the forseeable future, he said.

"We're never going to be able to bring to you a budget that is lower than the previous year," Weinberger said.

Sounding another grim note, Weinberger said that his own study of what the Soviets have done and are doing in military preparations leads him to "believe they feel a nuclear war can be won."