Abstract: The state-of-the-art about surface flashover across semiconductor all over the world is reviewed. Different types of electrode configuration are employed and influence factors on flashover characteristics are discussed. The process of flashover is divided into three phases. The self-defining equivalent conductance parameter is introduced as a criterion. Through measurement and simulation of thermal process of the current filament, it is believed that the temperature of filament channel could approach the melting point of the semiconducting material, which supports the hypothesis that temperature of flashover channel is high enough to arouse desorption of gas molecules. Furthermore, the experimental results of gas desorption primarily prove that there could be a channel outside the surface