Abstract: Based on Reynolds stress model(RSM)，the gas-phase flow field in the cyclone separator with volute inlet was numerically simulated and the asymmetric characteristics of the flow field were analyzed.The results indicated that the gas-phase flow field was asymmetric in tube space and cone space, especially in annular space.Because of the asymmetric inlet structure,the axial center of the gas flow vortex deviated from the geometric center of the cyclone.The deviation and direction in different axial positions were different, and the maximum deviation was approximately 0.07R.This caused remarkable asymmetry of radial velocity profiles of the gas-phase flow field.The above stated results were in fair agreement with the experimental data from literature.