Congress has given the Department of Housing and Urban Development $7.8 billion more than it asked for in its fiscal 1986 budget request, with nearly all of the extra money designated to provide housing for the poor under programs the Reagan administration wanted to kill or put on hold for two years.

The legislation, which the president signed recently despite the disparity between the amount approved by Congress and the figure he requested, calls for 97,000 more units of assisted housing than HUD now provides.

The administration asked for a two-year moratorium on new housing for the poor, bringing charges that the White House was trying to trim the swollen budget deficit at the expense of the country's poor.

A total of $14.7 billion was authorized for HUD next year, including money for community development, public housing operations, research and other programs in addition to assisted housing.

The budget authorization is somewhat misleading, however, because the total figure includes amounts that will be spent in coming years for projects started this year, housing experts said.

The legislation earmarks $10 billion to fund 97,000 new units of assisted housing through rental assistance programs, rehabilitation of housing and construction of 5,000 units of new public housing, 2,000 units of Indian public housing and 12,000 units for the handicapped and elderly.

Last year, Congress appropriated money for 100,000 new assisted housing units, also more than the administration wanted.

Urban Development Action Grants (UDAG) were rescued by Congress, which rebuffed an administration proposal to kill the grants as part of an effort to eliminate all local economic development subsidies.

The program was cut back by 25 percent over last year, however. The urban grants go to "distressed" cities for use in projects that will attract private investment and provide jobs. Community Development Block Grant funds, which pay for a variety of development projects in small and large communities, also were cut by 10 percent.

In addition to the money for building new public housing units, funds were voted for 32,000 so-called Section 8 certificates, 5,000 fewer than last year. The certificates cover the difference between 30 percent of tenants' income and fair market rents established by HUD.

Money also was appropriated to pay for the moderate rehabilitation of 10,000 housing units for low-income families.

Funding also was approved for 36,000 vouchers, under which low-income families find their own housing. A voucher covers the difference between 30 percent of family income and the HUD-established fair market rent for the area. A family is free to pay more than 30 percent of its income for rent, an option not allowed under the Section 8 program.

If the family pays less than 30 percent, it can pocket the difference.

HUD Secretary Samuel R. Pierce Jr. has said vouchers will enable his agency to "do more with less" in providing housing. Critics predict vouchers will lead to rent gouging, because the program rules do not prohibit property owners from charging more than fair market rents. Landlords participating in the Section 8 program were limited to HUD's fair market rents.

The agency relies chiefly on the vouchers and Section 8 certificates to house the poor, arguing that there is no shortage of housing, only a shortage of homes low-income families can afford, a problem the rental assistance programs can solve.

Low-income housing organizations argue that both problems exist, and "you can't address just one side of the problem," said Bill Wise, spokesman for the National Association of Housing and Redevelopment Officials.

He said Alexandria and Montgomery County are examples of areas with low vacancy rates in housing within the range of low-income families, even with the use of vouchers and Section 8 certificates.

Nearly $5 million the Senate proposed for a trial program in housing the homeless was eliminated from the final legislation, while $70 million was approved for emergency food and shelter services.

Public housing operating subsidies were cut from $1.24 billion last year to $1.21 billion in 1986, while $1.5 billion was voted to pay for modernization of public housing.