Abstract: With an aim to optimizing the structural design of H. M. cyclone's qualified medium feed pump for improvement of cyclone performance,an analysis is made of the flow mechanism inside the medium pump operating with offset-arranged short blades,based on the resistance characteristics of cyclone and from both mathematical and physical aspects. Following that,the laws governing the flow filed distribution are revealed through computational fluid dynamics analysis. Result of study indicates that the use of the short blades arranged in an offset manner can lead to improvement of state of fluid flow inside the pump,reduction of pressure pulsation and impact loss,effective control of the formation and development of the wake zone and increases of pump head and efficiency by respectively 3. 46 and 2. 66 percentage points. This well demonstrates the pump can work with much improved performance when operating with short blades arranged in a offset manner.