The utility model discloses an ash removing device which comprises a plurality of groups of mechanical arms, a movable frame, a motor, a screw, a slider and a push rod. Each group of mechanism arms comprises a plurality of mechanism arms. Each mechanical arm comprises a clamp and a brush disposed inside the clamp, and the brush wraps a heat exchanger light pipe. The plurality of groups of mechanical arms are fixed on the movable frame. The screw is connected with the motor. The longitudinal axial direction of the screw is parallel with the longitudinal axial direction of the heat exchanger light pipe. The thread in the slider is matched with the thread on the screw. The slider sleeves the screw. The slider is driven by the rotation of the screw to move along the longitudinal axial direction of the screw. One end of the push rod is fixed on the slider, and the other end thereof is fixed on the movable frame. The slider moves along the longitudinal axial direction of the screw to drive the push rod and the movable frame connected with the push rod to move along the longitudinal axis of the screw. The ash removing device has the advantages that the ash accumulated on the surface of the light pipe can be removed, and the heat exchanging efficiency of a heat exchanger is increased greatly.