In the sharpest rise in four years, serious crime in the District of Columbia increased 23 percent during the first three months of this year compared with the same period of 1978, D.C. police said yesterday.

Crimes against persons-including homicide, rape, robbery and assault-rose 18 percent. Crimes against property-including burglary and theft-spurted 25 percent, official figures showed.

Surprised by the increase, Police Chief Burtell M. Jefferson told reporters he "laid down the law" to field commanders, and the rate of increase for all crimes during April dropped to 6 percent.

Jefferson said its was "strictly a co-incidence" that the 23 percent increase came during Mayor Marion Barry's first three months in office.

He blamed unemployment-chiefly among youth-and weather conditions, along with the Mall demonstration by farmers in February and the teachers' strike in March, which forced the department to transfer hundreds of officers away from street patrols.

Barry's press secretary, Florence Tate, said the mayor was concerned by the rise in crime but has confidence in Jefferson, who was appointed chief by former Mayor Walter E. Washington late in 1977.

Barry also said that the increase in crime began in December 1978, the month before he took office. The December increase was 14 percent above the prior year.

Barry's office announced that the mayor will join Jefferson today in a news conference announcing numerous police personnel changes, not including the chief.

Departmental sources reported the changes will include eight promotions of high-ranking officers and a major reshuffling of assignments, including command changes in probably four of the seven police districts.

The increase in crime during the first three months of this year was disclosed at a hearing of the Senate D.C. appropriations subcommittee, which is considering the $104.6-million police budget for the 1980 fiscal year.

Hearing the figures, Sen. Patrick J. Leahy (D-Vt.), the subcommittee chairman, said Washington's reputation some years ago as a crime capital is "a stigma that has stuck with it" unfairly.

Jefferson said FBI figures showed the city's crime rate ranked 18th in 1978 among the nation's 26 largest cities.

He told Leahy that, on seeing the recent increase, he ordered district commanders to make better use of personnel to curb crime.

This year's 23 percent increase in the January-March quarter was the largest since mid-1975, when there were almost identical increases during two quarters of the year. From then until late in 1978, a decrease was reported, with only minor variations.

Offenses during the first three months of this year totaled 13,660. They included 50 homicides, up 35 percent; 87 rapes, up 47 percent; 1,833 robberies, up 18 percent; 623 aggravated assaults, up 15 percent.

In crimes against property, burglaries totaled 3,429, up 31 percent; larceny thefts totaled 6,740, up 22 percent, and auto thefts totaled 868, up 23 percent.

Geographically, the crime increase was spread fairly evenly across the city, with the 6th District leading with a 33 percent rise. That district covers far Northeast beyond the Anacostia River, an area that roughly coincides with Ward 7.

The 3rd District, an area north of downtown that includes the center of the city's prostitution and drug trade, showed a 9 percent rise, the city's lowest. The 2nd District, west of Rock Creek Park, was up 23 percent, almost entirely in property crimes.

One key assignment slated for announcement today is that of Assistant Chief Maurice T. Turner Jr., who is expected to become head of field operations, the department's No. 2 post. He would replace Bernard D. Crooke, who retired recently to become police chief of Montgomery County.

Police sources said the two top promotions today are likely to go to deputy chiefs Marty Tapscott of the 1st District and Charles E. Rinaldi of the 3rd District, slated to become assistant chiefs.

Tapscott reportedly will be replaced by Insp. Albert W. Ferguson and Rinaldi by Deputy Chief Theodore R. Carr, who is being moved from the 6th District. Deputy Chief William R. Dixon would move from the 7th to the 6th District, to be replaced in turn by Insp. James K. Kelly, now the 7th District night commander.

Insp. Roland W. Perry, police finance officer, is expected to become deputy chief in charge of the youth division. Its present head, Deputy Chief Herbert R. Horwitz, is expected to retire.

Capt. Isaac Fulwood Jr., Perry's assistant, is expected to replace him. Capt. Fred Thomas, head of the robbery squad, is likely to move to field inspections with a promotion to inspector. Also expected to be promoted to inspector is Capt. Edward Kreilis. CAPTION: Picture, Chief Jefferson discusses latest crime figures at press conference yesterday. By James A. Parcell-The Washington Post