One hundred low-income families in the District will get federal rent subsidies under an experimental program that ties the aid to local efforts to get young, single parents working, Mayor Marion Barry announced yesterday.

The District was chosen by the U.S. Department of Housing and Urban Development as one of 78 sites for the $25 million demonstration project, which will provide housing certificates to 5,000 single parents nationwide.

"Our goal is to . . . do all we can with job training, with education, with stimulation, with anything else we can do to get people off the treadmill of poverty, to get them off of government assistance into 'workfare,' " Barry said at a press conference.

Even with the new certificates, the Reagan administration has cut back dramatically on new awards of rent subsidies under the so-called Section 8 housing program, according to city figures.

In 1980, the last year of the Carter administration, 503 new federal housing certificates were awarded to the District.

That compares with a total of 151 during almost four years of the Reagan administration, a D.C. housing department spokesman said.

The 100 certificates under the experimental program will have a life of 15 years, with the intent that original recipients will become self-sufficient so that the subsidies will be available to others in the future.

The subsidies will have a total value of $500,000 in the first year.

Barry said yesterday that the District needs more help in creating affordable housing.

"In some communities, they have an excess of housing units, and vouchers and certificates will work.. . . In Washington, we need money for rehabilitation," Barry said.

"On the other hand, these 100 certificates will help. Everything helps."

City officials said that about 6,000 District residents will be eligible for the new housing certificates. Income ceilings will be the same as for current Section 8 assisted housing: a maximum $16,100 for a family of three, for example.

A recipient must be a single parent aged 21 to 25, with one or two children under 10.

The family would pay no more than 30 percent of its income and the certificate would be worth the rest of the family's rent at appropriate Section 8 housing, where a certain fair market value has been established.

Families chosen for the program will receive an array of other services designed to make them self-sufficient, including job training, child care and transportation.

A self-sufficiency program will be announced in about two weeks, said D.C. Department of Human Services Director David Rivers.

The city does not plan to create new services or spend more money in connection with the new housing certificates, but will focus on getting each of the 100 families into the kinds of programs that fit their particular needs, Rivers said.

The mayor also announced a new task force of various department heads, labor and business leaders and community groups to oversee the project.

In Maryland, St. Mary's County will receive 30 of the demonstration housing certificates.

In Virginia, Newport News will get 78, and Hampton will get 75.