Polyimide (PI) film is widely used as the insulation between coils in generator, where partial discharge (PD) may occur to cause the insulation breakdown. Fluorination is considered as an effective method for surface modification of polymer materials to change its electrical properties. In this study, to study the effect of fluorination on the PD behaviour of PI film used as magnet wire insulation, the samples of magnet wire were covered by PI film. Samples were fluorinated in a reaction kettle using the F₂/N₂ mixture for different time. The non-fluorinated and fluorinated samples were subjected to partial charges under alternating electric field. A wideband detection system was used to detect PD waveform and record discharge phenomenon. The experimental results indicate that the direct fluorination has great effects on the surface charge accumulation and the decrease in PD intensity. The magnet wire fluorinated for 45 min shows the highest PD inception voltage, the lowest intensity of successive discharges and the smallest number of discharge pulses.