The invention provides a mixed flow fan, which comprises a driving motor, an impeller wheel, a wind-sock, a guide vane cylinder and a guide vane, wherein a wind inlet side of the wind-sock is equipped with a cover plate, the cover plate covers a part area of the circumference of the wind inlet side of the wind-sock to reduce the actual wind entering area of the wind inlet, and the diameter of the impeller wheel still keeps adapted to the original wind inlet; the cover plate is ring and of which a round through hole in the middle is concentric with the wind-sock, and the inside diameter of the round through hole of the cover plate is less than that of the blade of the impeller wheel; a tubular external mouthing is arranged in the inside diameter of the through hole in the middle of the cover plate, the axis of the external mouthing is parallel to that of the wind-sock, and the contour of the mouthing in a longitudinal section passing the medial axis of the wind inlet is streamline. The preferable embodiment of the invention further adopts measures to improve the wind quality of the heat dispersion wind, and adopts shock proof measures to reduce the shock of the fan. The mixed flow fan is particularly suitable for being used in heat dispersion occasions of locomotive inverters, or can be applied to other similar occasions.