The House Appropriations Committee yesterday handed President Reagan his third victory in a week on the MX, voting 30 to 26 to release $625 million to flight-test the missile and modify Minuteman silos to accept it.

The vote came after Rep. Jack Edwards (R-Ala.), ranking minority member on the Appropriations subcommittee on defense, told members that "the president has in fact modified his position" on arms control, as some moderates had demanded before they would approve the new missile. "The need is to go forward now" with deployment of the MX, Edwards said.

Reagan opened his news conference last night by hailing the "bipartisan consensus on arms control" he said was emerging. "I congratulate both Appropriations committees for their bipartisan approval of the MX 'Peacekeeper' missile," he said. "I look forward to prompt approval of this vital program by the full House and Senate. It will be one of the most important arms control votes of the 98th Congress."

Last year, in a major reversal for Reagan, the $625 million was put on the shelf by Congress until the administration could come up with an acceptable way to deploy the MX. Presidents have rarely been beaten in Congress in modern times on strategic weapons votes; Reagan has said he needs the MX to shore up U.S. defenses and squeeze an arms agreement out of the Soviets at Geneva.

"What we're doing is approving the basing mode" recommended earlier this year by a presidential advisory commission headed by Brent Scowcroft, Edwards said. This calls for placing 100 MX missiles in Minuteman silos at Warren Air Force Base in Wyoming and Nebraska. Edwards said the question of whether to put the MX in production would come in votes on other bills.

But Rep. Joseph P. Addabbo (D-N.Y.), chairman of the defense subcommittee, said the Pentagon would find a way to use the $625 million for production. "We are voting for procurement of the MX," Addabbo thundered in a vain attempt to keep the committee from releasing the funds.

Last year Addabbo failed on a 26-to-26 tie in committee to delete $988 million from the defense appropriations bill to buy the first five MX missiles. He prevailed later on the House floor in part because members had doubts about the so-called Dense Pack basing plan the administration was advocating at the time.

That floor vote was what prompted Reagan to appoint his bipartisan advisory commission and start over on the weapon.

Dense Pack involved bunching the MXs on the theory that incoming Soviet warheads would destroy each other as they tried to blow up the missile field.

The Pentagon, Addabbo said, is "continuing the Dense Pack" by its plan to put 69 MX missiles in Minuteman silos in Wyoming and 31 in Nebraska. The missiles would not be spread far enough apart to survive if attacked, he said.

Addabbo offered a resolution to deny the Pentagon the $625 million. "Under my resolution, I say stop. I don't believe the Congress should have to pay $23 billion"--Addabbo's estimate of what the MX deployment would cost--"to get that kind of promise out of the president," meaning the arms control promises Reagan made in letters to members last week, including trying to negotiate an agreement to retire old missiles whenever new ones were deployed.

But Rep. Norman D. Dicks (D-Wash.) argued in support of the funds that it is time for lawmakers to "find a middle ground and move the country off dead center" on strategic arms. He termed Reagan's letter to him and other members of the House a "strong" one in which "the president is committed to the small missile."

The Scowcroft commission recommended that for the future the Pentagon look to a small missile instead of large ones like the MX. Some theorists see such a switch from large to small as a step toward arms stability.

Rep. Bill Green (R-N.Y.) asked his colleagues: "Are we going to spend this enormous amount of money on a weapon that doesn't work?" Rep. Les AuCoin (D-Ore.), in joining Green's plea for stopping the MX, said: "There is no survivability. You can't use it on first strike," because that is against national policy.

"And it won't be any good to us for second strike" because the MX would not survive a Soviet attack, he said. "Then why the hell are we spending $20 billion on this thing? It represents an invitation to strike first."

Rep. Vic Fazio (D-Calif.) said the Scowcroft report and the president's recent accommodations to Congress on arms control "provides us with a way to restore some of the trust in our own government. There is no question but that the president has made some movement toward us." Twelve Democrats joined 18 Republicans in favor of releasing the funds yesterday. Twenty three Democrats and three Republicans voted against. Earlier, Addabbo's subcommittee had voted in favor of the funds, as has the full Appropriations Committee in the Senate.

While Fazio was making that statement, Defense Secretary Caspar W. Weinberger was before the House Foreign Affairs Committee answering questions about why he had said there was "nothing basically new" in the letters Reagan had sent emphasizing his commitment to arms control. Weinberger said his statements in that regard had been "misinterpreted or misquoted."