Abstract: The mixture multiphase model combined with the RSM(reynolds stress model) and kinetic theory of granular flow for high concentration multiphase flow was used to simulate the particle volumetric concentration distribution and separative efficiency in a hydrocyclone for drip irrigation system. The distribution situation and separating effecting of different diameter particles concentrating the hydrocyclone was obtained. The small diameter particles were mainly distributed in the region of inner vertex and had higher separation efficiency. While the big diameter particles were mainly distributed in the region of outer vortex and had poor separation efficiency. The separative efficiency computed by the mixture multiphase model was in accordance with the Eula multiphase model. Then, the influence of the entrance velocity and concentration on the separative efficiency was analyzed. The simulation results showed that the mixture multiphase model was available for the numerical simulation of multi-phase flow in the hydrocyclone. The results have great importance to the choice and optimal structure designing of hydrocyclone for the drip irrigation system.