Abstract: In addition to preventing debris in liquids pumped from spreading, expellers which are extensively used in all kinds of slurry pumps perform two other functions, i.e., reducing liquid pressure at seals and balancing axial thrust acting on impellers so as to reduce axial loads for bearings. Both functions are closely pertinent to reliability and life span of pumps and are exclusively determined by the geometry of expellers. The authors developed two programmers to find expeller dimensions for their expected aims. Based on pressure distribution within a rotating water body and mathematical analysis, the paper presented the calculating principles and processes for determining the geometrical parameters of two kinds of expellers, and derived several equations for design practice. The results obtained will be beneficial to the improvement of slurry pump reliability and performance.