Abstract: Surface flashover of insulators is widely applied in pulsed power technique. In the ion diode, polyethylence (PE) film is often used as anode foil, for it's abounding in hydrogen. As a flashover ion source, the formation of anode plasma influences the quantity and quality of ion beam seriously. A set of apparatus for studying flashover behavior of PE film in vacuum and it's measurement system are developed in our work. The experiment results of three PE films with difference thickness under impulse voltage of about 100kV, 40ns are presented. For the 90 and 65μm PE fil, if the maximal electric field be up to 150.5kV/cm and 145.3kV/cm respectively, flachover will occur. The luminescence phenomenon of film surface is also studied preliminarily.