The invention discloses a pressure expander of a centrifugal compressor. The structure of the pressure expander is improved, and high application value is achieved for further improving working performance of the pressure expander. A short blade is arranged in runners of every two adjacent long blades; the front edges of the long blades are curved surfaces and are arranged obliquely, and the included angles between front edge lines and the central axis of a wheel disc are 6 degrees to 8 degrees; the radius of curvature of the front edges of the long blades is gradually increased from the wheel disc to a wheel cover; each long blade is provided with three broken-line-shaped channels penetrating through a corresponding pressure surface and a corresponding suction surface; tail edge wing tips are arranged on the portions, located on the pressure surfaces, of the rear edges of the long blades. Occurrence of separation of airflow on the surfaces of the blades is restrained through the short blades in the runners of the adjacent long blades; the pressure differences between the pressure surfaces and the suction surfaces are reduced through the broken-line-shaped channels, the adverse pressure gradient is reduced, and separate airflow on boundary layers of the suction surfaces at the tails of part of the blades is effectively blown away; increase of wing tip vortexes generated by the pressure differences between the suction surfaces and the pressure surfaces on the rear edges of traditional wing-type blades can be restrained through parabola-shaped winglets on the tail edges.