Aero-engine compressor is seriously threatened by the ingestion of liquid water. This article aims to deeply study the influences of different water contents and droplet diameters on the unsteady performance and thermodynamic parameters of compressor through frequency spectrum analysis. The accuracy of numerical calculation for compressor performance is verified by experimental data. Results show that the compression performance will be reduced and the unsteady fluctuations inside compressor will be aggravated after water ingestion. For some important parameters, such as mass flow rate, total pressure and temperature ratio, as well as efficiency, their main frequencies are changed from the original blade passing frequency to the rotor passing frequency (RPF), and their amplitudes are also significantly amplified. The working point of compressor will experience the nonoptimal state with large amplitude and period for a long time, which is not conducive to the stable operation of the compressor. Moreover, within the range of 2% to 8% water contents and 50 to 150 mu m droplet diameters, the fluctuation amplitude is correspondingly exacerbated with the increase of water content or droplet size, but its main frequency is maintained at RPF. Particularly, the tip clearance is the most sensitive region affected by water ingestion where the fluctuations of static pressure and temperature are the largest. The point that water content has a greater influence on the performance fluctuation of compressor is also confirmed in this article.