The unemployment rate among non white teen-agers in the District of Columbia dropped slightly last year but was 14 times higher than the rate for white youths in the city, according to a new study by the city Department of Labor.

The jobless rate for nonwhite males and females aged 16 through 19 in 1978 was 45.6 percent of those who sought jobs, a drop from 48.5 percent in 1977. The comparable rate for white teen-agers last year 3.3 percent unemployed, down from 11.2 percent in 1977.

However, the unemployment rate for white jobseekers in the city actually increased last year, to 3.8 percent, compared with a 2.5 percent rate in 1977.

For nonwhites of all ages, the unemployment rate was 10.3 percent last year, a drop from 12.2 percent in 1977.

The overall jobless rate for the District last year was 8.5 percent, down from 9.7 percent in 1977.

Rufus Daniels, a labor economist for the agency that made the study, said the decline in joblessness among young nonwhites was so small as to be statistically insignificant.

According to the city labor department report, there were 8,000 nonwhite teen-aged male jobseekers last year, 47.5 percent of whom did not find jobs. There were 5,000 females in the same age group, 42.4 percent of whom were jobless.

However, there were only 2,000 white males in the same age group, 3.3 percent of whom could not find jobs. Statistically, there was no joblessness among the 1,000 white females in the same age group.