Abstract: In order to further investigate the unsteady characteristics of the transonic axial compressor blade tip flow field, the unsteady simulation of the NASA Rotor 35 is carried out to get the performance in different mass flows. Based on the simulation results, the blade tip flow field is decomposed by using proper orthogonal decomposition (POD) method. The results indicate that POD method can decompose the blade tip unsteady flow according to their energetic values and it can capture the fluctuation frequency of the blade tip unsteady flow field, the corresponding modes show large scale disturbance characteristic structure in the blade leading edge, moving along the circumferential direction. By reconstructing the flow field, the disturbance feature structure propagating along the circumference is reproduced visually.