The unsteady vortices interactions in different scales of space and time for the compressor flow fields under inlet distortion are major influential factors to the performance of compressor.Aboundary condition model for unsteady numerical simulation under inlet circumferential distortion was presented in this paper.A 3-Dunsteady numerical simulation was conducted based on the boundary condition model.The results show that the model could reveal the unsteady interaction between wide scale total pressure wave resulting from inlet distortion and unsteady separation flow field in the rotor passage.This model provides a simple method for 3-Dunsteady numerical simulation under inlet circumferential distortion.