The invention discloses a coal cinder removing device used for coal seam gas mining. The coal cinder removing device comprises a connector, a first stage spraying and receiving section, a first stage cyclone centrifugal separation section, a second stage spraying and receiving section, a second stage cyclone centrifugal separation section and a final stage separation section. The final stage separation section is provided with a coal cinder outflowing opening. The first stage cyclone centrifugal separation section and the second stage cyclone centrifugal separation section are both provided with well liquid outlets, and the well liquid outlets of the first stage cyclone centrifugal separation section and the second stage cyclone centrifugal separation section and a well liquid outflowing opening of the final stage separation section are mixed and communicate with a liquid inlet of a liquid pump. The coal cinder removing device can well remove coal powder and coal cinders in well liquid and can effectively prevent the pump sticking and blocking phenomena, of a suction pump, caused by coal powder and coal cinders. The coal cinder removing device adopts two-stage separation, is additionally provided with final stage separation, can remove 95% or above of the coal cinders even the coal powder, is high in separation efficiency, can completely achieve supply to the suction pump and cannot cause low load operation of the suction pump.