Chairman Joseph P. Addabbo (D-N.Y.) of the House Appropriations subcommittee on defense said yesterday that he will try to cut $30 billion from President Reagan's new defense budget.

He set his target after Defense Secretary Caspar W. Weinberger told the subcommittee that cutting the fiscal 1984 military budget "would do severe damage to the security of the country."

The $30 billion would be in spending authority rather than money actually to be spent by the Pentagon in the year beginning Oct. 1. Addabbo estimated that it would translate into a spending cut of about $15 billion for the year.

The part of the Pentagon budget before Addabbo's subcommittee totals $265 billion, which includes the big-ticket items but not military construction. Addabbo said his cutting would zero in on Army Pershing II missiles, Navy nuclear-powered aircraft carriers, Air Force MX intercontinental missiles and B1 bombers.

Asked what his chances were of making a $30 billion cut, Addabbo replied, "In the subcommittee, questionable. On the floor, pretty good possibility." He said that if he loses in subcommittee and the parent Appropriations Committee he will renew his budget-cutting campaign on the House floor. "I'll go where the people speak," Addabbo said with a smile.

Addabbo, after years of defeat, won big last year in his efforts to cut the Pentagon budget as the House deleted funds for the MX and Pershing missiles. His attempts to delete money for building two more Nimitz-class aircraft carriers failed, however.

Rep. Jack Edwards (R-Ala.), ranking Republican on the Appropriations subcommittee, told Weinberger yesterday that he had understood the two carriers requested last year would be the last, only to discover another Nimitz proposed for fiscal 1988. Weinberger said the Pentagon is not committed to buying another Nimitz, but included it in the five-year defense plan in case renovation of existing ships founders in the future.

Addabbo and several other subcommittee members warned Weinberger that if he does not volunteer cuts in the fiscal 1984 budget Congress will impose them on its own.

Rep. W.G. (Bill) Hefner (D-N.C.) told Weinberger, "We're losing our grass-roots support for spending." He urged Weinberger to moderate the growth of future defense budgets to preserve public support.

"We're not going to be able to sustain" the projected growth of the defense budget "unless the economy improves," Hefner said. Cutting defense spending would help improve the economy and thus give the Pentagon budget a more solid base, he said.

Weinberger repeated to Hefner and others his general theme that the Reagan military budget represent the amount vitally needed to combat the Soviet threat. He chided lawmakers who said they were "for defense, but," calling them "defense buts."