Abstract: In off-design conditions the corner separation can become severe thus lead to strong non-equilibrium turbulent state.To correctly simulate the flow field the transport process of non-equilibrium trubulence must be predicted reasonable.Based on the analysis of turbulence transport nature at different operating conditions in compressor corner separation flows,a modification method on the relationship between the production and dissipation of turbulence viscosity to improve the simulation ability of Spalart-Allmaras(S-A) model at off-design condition in compressor flow was proposed and studied by numerical simulation.It shows that comparing with experimental data and academic analysis the modified S-A model could give out more reasonable and correct predictions than conventional S-A model.