A lot of the federal alphabet soup would disappear if Congress were to go along with President Reagan's proposed new fiscal 1986 budget.

UDAG, EDA, SBA, REA, FmHA, and ARC are a few of the governmental acronyms -- cherished by big-city mayors, farmers, urban dwellers, commuters and businessmen -- that would die in the administration's deficit-slashing efforts.

Some of these programs, which affect mainly the middle class, have been the subject of administration assaults before, with little success.

These programs are among those slated for the ax:

* The $574 million subsidy for Amtrak, the national passenger train system. Amtrak failed its original goal of profitability, the administration argues, and the average $35 per-passenger subsidy is too much.

* The Urban Development Action Grant (UDAG) program, a popular holdover from the Carter administration that provides start-up funds for commercial construction. By gutting UDAG, the administration said it would save $2 billion over the next three years.

* The Job Corps, a federal job-training program that the administration argues is not effective or cost efficient. If the program continues, the administration said, it would cost $15,200 to train each of 40,500 enrollees.

* The Small Business Administration, which provides credit and low-interest loans to 21,500 businesses. The government should be more of a cheerleader for small business than a "Daddy Warbucks," the administration argues. Besides, the budget proposal said, plenty of private-sector loan money is available.

* General Revenue Sharing, which spreads nearly $4.6 billion a year in federal largess among 39,281 local governments. The administration argues that revenue sharing no longer can be justified while state and local governments have surpluses and the federal government is swimming in a sea of red ink.

* The Appalachian Regional Commission and the Economic Development Administration. These resilient agencies, designed to stimulate economic development, have survived earlier budget assaults. The administration said it wants to get rid of them as part of a government-wide effort to eliminate local development subsidies.

* Most of the subsidized loan and grant programs of the Farmers Home Administration, a mainstay of farmers and businessmen in rural America, that financed more than $10 billion of water and sewer projects and community facilities in the past decade. In the future, rural areas would receive assistance through a block grant program of the Department of Housing and Urban Development (HUD).

* The Export-Import Bank's direct loan program, which has aided many U.S. corporations that do business overseas. The administration wants the bank to boost its program of loan guarantees and quit making direct loans. This is in line with the Reagan policy of placing greater reliance on private-sector financing.

* Air carrier subsidies, established in 1978 to provide financial assistance to communities as they adjusted to the impact of airline deregulation. The government has spent $460 million in subsidies. "To provide further subsidies to cities currently receiving them would turn a temporary transitional program into a permanent entitlement," the administration contends.

* Health professional training subsidies, first granted in the early 1960s in response to a serious shortage of doctors, nurses and other health specialists. Today, the administration argues, there is a glut of trained medical experts and the subsidy no longer is needed.

Reagan's budget proposes many other cuts or freezes that stop just short of killing programs. The Urban Mass Transit Assistance program, for instance, would be slashed next year by $768 million, with additional cuts planned that would bring the total to $4.2 billion within three years.

"Federal support for a local function like mass transit is unjustified," the budget document says. "It is unfair to the many taxpayers who pay for it and get nothing in return, and its availability reduces local incentives to make sound economic choices."

Reagan wants to squeeze the Power Marketing Administrations, a group of government-financed businesses that sells hydroelectric power generated at 123 federally operated dams by cutting outlays by $1.5 billion and forcing the hydroelectric operations to catch up on their loan repayments, even if that means boosting electrical rates. The PMA sells 6 to 8 percent of all electricity generated in the United States.

The president also wants to phase out the Rural Electrification Administration (REA) low-interest loan program over the next five years. Since 1936, more than $61 billion in federal assistance has been provided to rural electric utilities and telephone systems.

Federal soil and water conservation cost-sharing programs also would be eliminated.

A $384 million Maritime Administration subsidy for U.S. shipbuilders would be eliminated. Profit-making publications and companies as well as national political committees would lose federal subsidy for their postal rates.

The administration would declare a moratorium on U.S. oil stockpiling in the Strategic Petroleum Reserve. The SPR, designed as a defense against oil-supply interruptions, is expected to contain about 489 million barrels by 1986.

The president seeks to phase out federal sewage-treatment grants to state and local governments by 1990. The Environmental Protection Agency (EPA) would receive $2.4 billion in grants next year -- the same amount it has received since 1982. Future funds would have to be used only to complete existing projects.

The administration also wants to do away with grants for energy conservation and for weatherizing school buildings, hospitals and the homes of low-income families within five years.

The government will spend about $191 million on weatherproofing projects in 1986. The administration proposes to cover those costs with funds recovered from petroleum companies that violated the old oil price-control program.

Other programs facing elimination under the budget proposal include the Legal Services Corporation and the work-incentive program.

One of the few proposed budget increases is a substantial one in funds for the "Superfund," which assists states in cleaning up waste dumps.

The administration also pledged to introduce legislation that would greatly expand the national effort to clean up abandoned waste sites.