A dust collector with a function of secondary collection is composed of a bottom base,an air guiding box installed above the bottom base and bored with a suction hole and a dust collecting hole at its upper and bottom surface respectively, a guiding device set inside the air guiding box, a filtering bag fixed on the guiding device, and a dust bag sealed with the lower dust collecting hole of the air guiding box. In using, dust can be drawn in by a blower to enter the air-guiding box. With a secondary filtration to prolong a service life of the filtering bag.