Abstract: Three-dimensional numerical simulations were conducted to analyze the flow field in a single-stage transonic compressor Stage 35.Firstly,three kinds of gridding were modeled to investigate their prediction accuracy on overall performance and blade-element curves.The criterion for choosing the optimum gridding is that the prediction matches best the experimental data.Then,the internal flow filed of the optimum gridding was analyzed to find out the most probable influential factor of the flow stability;and it is found that low-energy fluid near pressure surface at rotor tip most likely induces the flow instability.As the mass fow rate reduces,the intensity and swirl ratio of the tip leakage vortex(TLV) increase with the blade loading.The breakdown of the TLV occurs due to the interaction of shock/TLV at the near-stall condition,thus most possibly leading to low-energy fluid accumulated near the pressure side of rotor tip passage.