The Comb Separator is composed of motor reducer, tank and magnetic roller. The magnetic roller is arranged in the shape of comb teeth. The motor reducer drives the magnetic roller for circular motion. After coolant with powder magnetic impurities enters the tank, the impurities will be absorbed onto the outer walls of magnetic roller, and separated by stainless steel plate(copper plate). Liquid with impurities will be screened and dried, and will finally be moved into the collecting tank by the scraper. This device is especially applicable for coolant treatment of grinders with tremendous flux and substantial impurities, like roll grinder, rolling wastewater treatment, and bearing grinding line.