The Justice Department sued seven nearly all-white Chicago suburbs yesterday, charging that they use residency requirements as a way of keeping blacks out of municipal jobs.

The government believes that no black has ever been a public employe of any of the suburbs, according to the suits filed by Assistant Attorney General William Bradford Reynolds, head of the department's Civil Rights Division. Not one of the 1,143 workers employed by the Illinois towns was black at the time of the department's investigation earlier this year.

Many cities across the country, including the District of Columbia, require municipal workers to live within the city, but they give newly hired employes a reasonable period to meet the requirement by moving in, Reynolds said.

However, the seven suburbs named in the suit in U.S. District Court in Chicago have no such "move-in" provision, Reynolds said. None will consider job applicants who do not live in that suburb or nearby towns, areas with few black residents.

The lawsuits name the Cook County municipalities of Berwyn, Dolton, Elmwood Park, Forest Park, Melrose Park, Niles and South Holland. They require that those applying for police and firefighter jobs have lived within town limits for as long as five years.

This is the second time the Reagan administration has challenged residency requirements based on race. An earlier suit charged the Chicago suburb of Cicero with excluding blacks from the city through discriminatory housing policies, which combined with a residency requirement barred them from city jobs as well.

Reynolds said that the Justice Department warned the seven suburbs that they were violating the law, but that local officials failed to negotiate acceptable hiring policies.

The department is seeking injunctions to halt the towns' hiring practices and require them to start recruitment campaigns to attract qualified blacks. The suits also would provide back pay and retroactive seniority for anyone who can prove he was denied a job because of race.