The invention is a tail gas dedusting device of a magnetic material presintering rotary kiln. The structure of the tail gas dedusting device comprises a screw feeder, the rotary kiln, a high-temperature dedusting chamber, a gas rapping hammer, an air flow regulating and increasing device, a water bath dedusting chamber, a draught fan, a cold dryer, an immersion type ultrasonic wave water dedusting device, a gas bubble generator, an ultrasonic signal generator, an ultrasonic transducer, spoilers, and a pulse dedusting device. The tail gas dedusting device has the advantages that multiple layers of metal screens are utilized to filter larger dust particles in tail gas, and the collected dust particles are used as raw material for utilization; the problem that dust in a longer pipeline is accumulated to block a pipe because of declining of the gas flow rate is solved; multiple kilns can be connected to one set of water bath dedusting chamber and the immersion type ultrasonic water dedusting device through pipelines; the water bath dedusting chamber can remove the dust in the tail gas; the gas bubble generator is utilized to cooperate with ultrasonic waves generated by the water tank internal bottom ultrasonic transducer connected with the ultrasonic signal generator, so that the dedusting effect is enhanced; and the arranged spoilers prolong the time of gas bubbles staying in water so as to further improve the dedusting effect.