A D.C. Superior Court judge has sentenced a 29-year-old Washington woman to serve three years in prison for prostitution--a sentence believed to be the longest imposed here for that crime in at least four decades.

Judge George D. Neilson ordered the lengthy sentence for Meko Chan, who has a criminal record of 88 prior arrests and convictions for prostitution since 1970, according to FBI records. Nielson said Chan has been a prostitute since she was 12 years old.

"I sympathized with her plight," Neilson said. "But if I imposed a light sentence on her, she's going to come out and do the only things she knows how to do . . . unless maybe she gets some training in prison for another job."

Neilson said he imposed the sentence in "the spirit of protecting the community and trying to straighten these people out so they can be useful citizens."

Assistant U.S. Attorney James N. Owens said yesterday he urged Neilson to impose a stiff sentence to "give notice to the army of prostitutes that will descend on Washington with the onset of warm weather." Owens said he wanted Neilson to tell prostitutes that the Shaw area would not tolerate "this invasion."

The sentence thus became the opening salvo in this year's battle against prostitutes by law enforcement officials, hotel owners and citizens who live in the residential neighborhoods--particularly around Logan Circle--where prostitutes congregate.

Neilson, who recently sentenced a drunken driver to a year in jail, said he hoped the lengthy sentence he gave Chan would "let people know we are going to deal firmly with this prostitution . If we are going to control this, then we have got to impose stiff sentences."

According to FBI records, Chan was first arrested as an adult in New York City. She had dozens of arrests there before apparently moving to the District in 1979. Her first arrest here was in September of that year.

A D.C. Corrections Department official said yesterday that Chan declined when asked if she would speak to a reporter. Her attorney, Richard Ringell, could not be reached for comment.

At the sentencing last Friday, Neilson said that he had received a letter that morning from Paul O'Neil, general manager of the Sheraton Washington Hotel and president of the Hotel Association of Washington, D.C. The letter, sent to all local judges, urged them to hand down stiff sentences for prostitution.

Neilson, a retired judge who handles cases on a part-time basis, said yesterday that each case had to be judged on its own merits and he was "not going to be stampeded" by pressure from the hotel association. But he said the letter illustrated the problems hotel owners face because of prostitution.

Neilson's action was lauded yesterday by hotel owners and residents of the Thomas Circle and Logan Circle areas.

O'Neil said he was "glad to see" the sentence because "we need all the help we can get." And Edward F. MacMillan, partner and managing director of the International Hotel at Thomas Circle in the heart of the "red-light" area, said he was "delighted" with the harsh sentence, which he said was "long overdue."

MacMillan said that he felt that if increased fines and harsh sentences were meted out on a regular basis, there would be some reduction in the amount of prostitution in the area.

"Hallelujah," said Logan Circle activist Barbara Rothenberg when informed of the sentence. Rothenberg, who has tried for years to pressure law enforcement officials to crack down on prostitution, said she didn't think Chan's sentence was too harsh, "considering the amount of money she Chan has made over the years."

The maximum penalty for prostitution here is 90 days imprisonment and a fine of up to $300. But Owens said prosecutors have the option of asking for increased imprisonment for repeat offenders. Two prior offenses allow prosecutors to ask for triple fines and imprisonment for each offense. In addition, Owens said, prosecutors can ask for an additional year in prison for every offense committed after a judge has released a defendant pending trial.

In this case, Owens said, Chan, who was facing five separate charges, pleaded guilty to three and faced a maximum of one year and nine months in prison on each charge and a fine of $900 on each count. Neilson sentenced Chan to one year on each count, the sentences to run consecutively, but imposed no fine in the case.