To research the effect of haze on external insulation performance in depth, this paper investigates the related results at home and abroad. The formation and sedimentation of haze, the simulation and its influence on power transmission devices external insulation performance are discussed and analyzed. The results show that haze is formed by human activities that produce a large sum of pollutants in a certain wet weather condition, the main discharge sort of insulator is surface flashover, the pollution flashover voltage is well decreased if haze sets onto the insulator surface or floats into the air gap between insulators. So in the area where haze appears frequently and insulators distribute dense, green jobs should be reinforced, and effective measures should be taken to prevent the influence of haze on power transmission devices external insulation performance to ensure insulators run safely, reliably and stably.