Abstract: The Computational Fluid Dynamics(CFD)method was used to simulate the flow fields and calculate the separation efficiency of air-liquid spiral separators with different structural parameters.The RSM turbulent model (Reynolds Stress Model), which abandons the isotropic eddy-viscosity hypothesis, was used to analyze the highly swirling flow fields in spiral separators.Random Orbit Model was used to simulate the traces of liquid droplets in the whole flow field.Based on the simulation, the effects of helical pitch and screw number on the separating performance were studied, which was further tested and verified.The results showed that the Reynolds Stress Model predicted successfully the characteristics of the flow and the simulated performances were in good agreement with those obtained by tests.It should be feasible to design the spiral separators based on the method of Design by Numerical Analysis.