Abstract: For researching on disc separator’s inner flow field, the numerical method was an important means to optimize the design. Aimed at lubricant disc separator, the numerical simulations of inner oil-fluid-solid separation process and separation efficiency were completed by using VOF multiphase flow model, RNG k-ε turbulence model and discrete phase model. The simulation results showed that laminar flow was in the discs space and turbulence folw was in the center hole and disc edge, and the inlet velocity had little influence on the result of oil-water separation but had a greater impact on the solid particles separation. The solid particles’ separation efficiency maximum relative error between the calculated and the measured was 1.5%, and when the rated capacity was 700 L/h and the inlet velocity was 2.5 m/s, the separation efficiency was 97.2%, which satisfied the design requirement. The results indicates that the three-phase flow analysis method is available, the method is very importance to optimize the structure design of disc separator. At the same time, it can reduce the time and cost required for experiments.