Major crimes increased about 7 percent in 1981 over 1980 in the District of Columbia, D.C. Police Chief Maurice T. Turner said yesterday. Robberies, spurred by what Turner called a glut of illicit drugs on the street, led the way with a 17 percent jump.

The rate of increase, however, slowed during the year, at least through the first 11 months, and appeared to be decelerating compared to the two preceding years as well.

Turner expressed cautious optimism at a press conference that various anticrime programs, including the city's now half-year-long drug crackdown and a more recent strategy of placing police "plants" in robberyprone convenience stores, is beginning to pay off.

Statistics for the first 11 months of 1981 show that a total of 61,457 major crimes -- homicide, rape, robbery, aggravated assault, burglary, larceny and auto theft -- were reported to police compared to 57,991 for the same period in 1980.

That's a 6 percent increase, but Turner said the final year-end figures will probably show a 7 percent rise, with December recording an upsurge in robberies.

Robbery squad detectives have already reported a preliminary year-end total of 10,423 robberies in 1981, a 17 percent jump over 1980. It is the first time the annual robbery total has topped 10,000 since 1971.

For the January-through-November period of 1981, police figures released yesterday showed homicides up 13 percent from 179 to 202; rapes down 7 percent from 411 to 382; aggravated assault up 7 percent from 2,965 to 3,160; burglaries up 4 percent from 14,782 to 15,300; larcenies up 5 percent from 28,449 to 29,739, and auto theft also up 5 percent from 3,288 to 3,435.

The overall 7 percent increase for the year anticipated by Turner is substantially less than the 13 percent jump in reported crime from 1979 to 1980 and the 11 percent increase from 1978 to 1979. Nevertheless, the numerical total of offenses for 1981 is expected to approach levels of a decade ago when annual totals sometimes exceeded 70,000. The greatest number -- 82,631 -- was recorded in 1969, a year after President nixon called Washington the "crime capital of the nation".

Turner said yesterday armed robbery continues "to be a very serious problem in this community... There are a lot of people out there with handguns."

To blunt this, he said, special teams of police plants have been deployed for the past two weeks in various business establishments that seem especially vulnerable to holdups. He said 40 to 60 stores have plants during weekdays and 75 to 80 on weekends.

He said armed robberies of commercial establishments have declined since the program started, but did not have figures immediately available.

Also, he said, he is drawing up a report for Mayor Marion Barry recommending transferring up to 100 desk-bound police officers to street duty to beef up the city's crime-fighting programs.