Blacks are continuing to gain in employment and promotions in the District of Columbia government, although the improvement has been slowed by recent cuts in the payroll, the D.C. Office of Human Rights reported yesterday.

The office reported women did not fare quite as well in employed last year as in 1975, the most recent previous report.

In fact, the report found, the proportion of women on the city payroll remained almost constant between 1968 and 1971 - hovering between 43 and 45 percent - while the proportion of blacks increased from 58.7 to 71.1 percent.

The city's population is about 75 percent black.

A summary of the report concluded that, on a statistical basis, "both blacks and women were not under-represented in overall D.C. government employment."

The report, which reflects the status of the city payroll on Jan. 1, 1977, is the newest in a series issued periodically since 1971. The Office of Human Rights, which prepared it, is charged with monitoring city hiring and promotion practices and enforcing rules again discrimination.

The proportion of blacks on the city payroll, which had increased by 1.9 percent from 1973 to 1975, rose only 0.6 percent to a total of 71.1 percent in the two years that followed, the report found.

However, the number of blacks as well as whites on the payroll declined between 1973 and 1975 as a result of congressionally imposed employment ceilings and a hiring freeze.

In general, the blacks were clustered more heavily in lower pay grade levels, and their proportion declined as grade levels increased. An exception was in the highest grades, GS-16 and GS-18, where blacks occupied 45 percent of the jobs last year, an increase from 40.3 percent in 1975.

The median salary for blacks last year was $13,582, for whites it was $16,702. That means the typical black earned 81 percent as much as a white on the city payroll.

James W. Baldwin, director of the human rights office, said this is largely the result of historic patterns.

Many of the upper middle-ranked jobs are held by whites who have been employed for many years, he said. In general, he noted, they will continue to hold those jobs until they retire, making way for promotions of lower-ranking employes.

The report showed that women accounted last year for 44.2 percent of city's employes, a decline of 0.2 percent from 1975.

Since 1968, the proportion of women in the top job grades has declined from 14 percent to 12.6 percent. However, the latter figure represents an increase from a low of 6.8 percent in 1971.

The median salary for women last year was $13,188 while that for men was $15,507.

The report said blacks accounted for 70.1 percent of new employes and 73.7 percent of those promoted between 1975 and 1977. Women accounted for 44.6 percent of new hires and 48.6 percent of promotions.

There were 255 Hispanic employes on the payroll last year, a 0.6 percent of the total, virtually no change since 1971.