Kitchen exhaust fan device

The invention discloses a kitchen exhaust fan device which comprises an outer frame; an inner frame is arranged in the outer frame; a double-shaft motor is arranged in the inner frame; a fan a is fixedly arranged on one of the output shafts of the double-shaft motor; a rotary shaft is arranged in the inner frame; a fan b is fixedly arranged at one end of the rotary shaft; a dustproof filter screenis arranged on one side of the outer frame; a plurality of retaining blades are arranged on the other side of the outer frame; a rotary rod is fixedly arranged at one end of each of the retaining blades; and a small-size motor is fixedly arranged in the outer frame. The kitchen exhaust fan device is reasonable in structure; when the retaining blades are in the closing state, rainwater and polypides can be prevented from entering the outer frame; the rotary rods drive the retaining blades to rotate together, so that the outer frame and the retaining blades form certain angles to blow lampblackout; the fan a rotates to