Nearly 70 percent of the households in newly built federally subsidized housing in the Washington area are headed by women, according to a new study by the Council of Governments.

The report, the first complete portrait of residents in subsidized housing here, found that the average family, a woman and one or two children, had an income of $6,000 a year--far less than the area's median income of $23,344 per household.

"We were surprised at how low the income levels were," said Scott Riley of COG, who prepared the study that surveyed 3,875 families in 39 projects scattered throughout Washington and the suburbs.

"The program really is serving those who need it most--those who could not afford housing in the general market," he added.

Congress, at the urging of the Reagan administration, has proposed to all but stop the federal government's 40-year-old program of building subsidized housing and substitute a system of housing vouchers.

Fifty-two percent of the residents surveyed were black and 75 percent of those households were headed by women, according to the study. The highest number of households headed by females was in Washington, the smallest in Fairfax County. In that county half of the residents of subsidized housing are families with both a mother and father present.

Subsidized families in Fairfax County also had the highest incomes of those surveyed. The median income level in Fairfax is $11,570 for subsidized families compared to $6,096 for those in Washington, $7,280 in Montgomery County and $5,493 in Prince George's County.

James Woolfork, who directs the District's subsidized housing program, said women, those who are elderly and those with growing children, make up a majority of the subsidized housing population because their incomes are usually lower than those of men.

The survey showed that subsidized households headed by men earned on the average about $2,500 more than those headed by women--$8,892 for families headed by males compared to $6,334 for those headed by females.

Households headed by a handicapped person had the lowest median annual income at $3,548 a year while two-parent households had the highest, $10,192. Households headed by an elderly person earned a median income of $4,633.

The survey also found the lower-income families are not moving from one area jurisdiction to another in search of subsidized housing.

The majority of families interviewed for the survey lived in projects built under the Section 8 program, the government's major housing subsidy program, since 1974. Residents pay 25 percent of their income as rent and the federal government makes up the difference between that amount and the amount needed to pay off the mortgage.

More than 10,000 Section 8 units have been built in the District and suburbs, but area jurisdictions report that thousands of families remain on waiting lists because the demand greatly exceeds the supply.

"The calls are coming in from people venting their frustration on us because we don't have the housing," said Joyce Siegal, of the Montgomery County Housing Opportunities Commission, echoing the comments of other area officials.