The invention provides an ultrasonic atomizing bag type dust removing device and a dust removing method. The ultrasonic atomizing bag type dust removing device mainly comprises a deduster, and is characterized in that: the lower part of the bag type deduster is provided with a plurality of fog inlets which are connected with an ultrasonic atomizer respectively; and a flow valve is arranged on each fog inlet connecting pipe. By utilizing the ultrasonic atomizing bag type dust removing device, superfine fog drops are injected into the deduster in the process of dust removal to obtain moist filter cakes with large voidage; the moist filter cakes are easy to shed, and can avoid secondary dust-raising phenomenon; the cakes with the large voidage can reduce the running resistance of filtering effectively, and is favorable for saving energy sources. The removing device and the dust removing method have the advantages of capability of reducing energy consumption in the filtering process, lesswater consumption, simple dust subsequent treatment process and convenient dust recovery, no secondary dust raising, reduction in running resistance in the filtering process, and improvement on trapping performance of filter materials.