Polyimide (PI) has good mechanical properties, heat resistance and low temperature performance, and thus shares a wide range of applications. Atmospheric pressure plasma jet was designed for polyimide films surface modification in this paper. The impacts of exposure time and gas ratio on the film surface morphology and property were studied. Scanning Electron Microscope (SEM) results prove that the treated film surface becomes rough and the contact angle decreases rapidly with exposing to plasma. The contact angle did not decrease anymore after extending plasma exposing time to 20 seconds Moreover the intensity of C=O absorption band increases as shown in the Fourier transform infrared spectroscopy (FTIR).