President Reagan won an easy victory on defense policy last night as the Democrat-controlled House adopted a $175.3 billion fiscal 1983 authorization bill that could produce history's largest peacetime increase in military spending.

The bill survived seven days of debate with scarcely a dent, and was passed 290 to 73. It now goes to conference with the Senate, which has passed a bill to authorize $177.9 billion for defense.

The House adopted one limiting amendment last night, in effect shaving the measure 1 percent across the board, from $177 billion to just over $175 billion.

Otherwise the administration prevailed, beating back amendments to cut funds for a series of controversial items in the Pentagon budget: MX and Trident missiles, C5B cargo jets, B1 bombers, civil defense, and troops stationed overseas.

Its string of victories were an indication that, while debate continues over exactly how large the buildup should be, the president has prevailed with his basic point that defense outlays must go up even in a time of retrenchment on domestic spending.

The president's success was assured by a determined majority of Democrats on the House Armed Services Committee, tacitly backed by the House Democratic leadership. Although one effort to cut funds for the MX came close, the only hostile amendment to pass was one cutting $54 million for nerve gas weapons, and it was put forward by a conservative Republican, Rep. Ed Bethune of Arkansas, in whose state the gas would be produced.

The legislation represents a $46 billion increase over this year, only $6.3 billion less than the president requested.

More than half the money is for the purchase of $88.7 billion in sophisticated new weapons, while $22 billion would go for research and development, $68 billion for operations and maintenance. The bill authorizes funds for 2.1 million members of the regular uniformed services, 989,000 reservists and 1.05 million civilian workers.

Despite the much-ballyhooed political clout of the nuclear freeze movement, the freeze's congressional champions were roundly defeated yesterday in an effort to cut funds for civil defense, which includes an elaborate evacuation plan for cities hit by nuclear attack.

"Civil defense will only be a Band-Aid over the holocaust," said Edward J. Markey (D-Mass.), whose amendment to cut the funding from $252.3 million to $144.3 million was defeated 240 to 163.

During a lively two-hour debate, Markey and other liberal Democrats argued that the civil defense program would create "the illusion" that nuclear war is survivable and winnable. He ridiculed plans which, he said, call for a civilian caught driving in an attack to dig a trench under his car and protect himself with nine sandbags, 50 feet of strong cord, a yardstick and four stakes which he would presumably have on hand.

Advocates, however, argued that the program, which would cost $4.2 billion over the next seven years, is indispensable during natural disasters such as earthquakes and tornadoes. It would also match the Soviets' extensive civil defense program, they said.

"We should make at least modest preparations to save what life we can" during nuclear attack, said William G. Whitehurst (R-Va.).

Virginia Republicans Frank Wolf and Stan Parris voted against the Markey amendment and in favor of the final bill. In the Maryland delegation, Michael Barnes (D) voted for Markey and for final passage. Steny Hoyer (D) voted against Markey and for the final bill, and Marjorie Holt (R) voted against Markey and was absent for the final vote.

An amendment sponsored by Patricia Schroeder (D-Colo.) to reduce the number of troops abroad from 490,000 to 250,000 by September, 1986, except in an emergency certified under the War Powers Act, failed 314 to 87.

Schroeder, one of the most persistent defense critics on the Armed Services Committee, found allies among some of the House's most conservative Republicans, who argued that the United States should save money by forcing Europe and Japan to shoulder a greater portion of their own defense.

"We're saying we're no longer interested in being the Wyatt Earp of this earth," Schroeder said. Harold S. Sawyer (R-Mich.) agreed, adding that we should stop giving Europe "a free ride to compete the pants off us internationally. They're sinking the economy."

An attempt to delete $671.7 from the Trident II missile program and add $26 million for the AXE anti-air base missile, a non-nuclear weapon that Thomas J. Downey (D-N.Y.) said would be more effective than the Trident, was defeated 312 to 89.