Abstract: With the rapid development of industry and agriculture, pollution has become a serious hidden danger to the safe operation of power grid, and flashover of outdoor composite insulators has occurred frequently. In order to understand the specific characteristics of flashover, the FZSW-10/4 composite insulator is used as the research object in this paper. Electric field and the temperature field were simulated, and the location where partial arc of insulator is more easily to ocurr is analyzed. The simulation results show that the conductive effect of salt density distort the electric field and makes the local electric field strength increase significantly. The temperature distribution characteristic of polluted insulators reveals the relationship between salt density and insulator surface temperature, which provides a theoretical basis for preventing insulator flashover.