Abstract: The IGV/rotor interaction phenomenon in turbomachinery has been resear ch focuses for years, but until now such researches have been restricted to qual itative description of flow phenomenon without theory instructions. So this very important unsteady phenomenon can not be included in turbomachinery design regi me to further improve turbomachinery performance. By the theory of flow instabil ity and receptivity, the rule of using this phenomenon to improve turbomachinery performance can be found. The IGV/rotor interaction phenomenon in a one stage l ow speed axial compressor was investigated experimentally. A 2D digital particle image velocimetry was used to acquire the quantitative flow field structure aro und the rotor with and without IGV. The rotor flow is evidently unsteady even un der steady flow condition. With IGV/rotor interaction, the rotor flow field was changed significantly. The intensity of rotor wakes was reduced, flow separation on rotor suction side was suppressed and the tip leakage flow was suppressed pe riodically. Besides IGV wake interaction and periodic variation in flow angle, d ifferent response of the rotor unsteady flow to different unsteady IGV/rotor exc itation frequency was decided to be the most important reason for the compressor performance changes.