Time-accurate simulations were performed to investigate the unsteady flow field at the tip region of a high-loading transonic axial compressor rotor at 98% design rotating speed. The results show that the oscillation of the shock is weak and the unsteadiness at the tip region is originated from the breakdown of tip leakage vortex and the shock/vortex interaction. The characteristics of tip leakage vortex were compared between design condition and near-stall condition. Detailed analysis was then made to emphasize the development of the behavior of tip leakage vortex at near-stall condition

where leading-edge spillage occurred intermittently. The breakdown of the tip leakage vortex after the shock contributes to a large blockage and also the stall disturbance of spike type.