The invention discloses a design method for a nonadjustable axial flow pump impeller with the characteristic of long blades and short blades. The method specially comprises the following steps that three-dimensional blade profiles of the long blades of the nonadjustable axial flow pump impeller are designed according to a streamline method; three-dimensional blade profiles of the short blades of the nonadjustable axial flow pump impeller are designed according to parameters of the designed three-dimensional blade profiles of the long blades; the designed short blades are arranged in the middles of flow channels formed by every two adjacent long blades at intervals, and the nonadjustable axial flow pump impeller with the characteristic of the long blades and the short blades is obtained. The problem of unstable fluid conveying caused by flow separation and swirling flow at the intersection of the suction surfaces of blades and a wheel hub near an outlet of an axial flow pump impeller during operation of the axial flow pump impeller is solved.