This work provides the effects of pollution on insulators in high voltage transmission line. Different stress such as electrical, mechanical and environmental stress on outdoor insulator has been discussed in this paper. Comparative performance of different insulators have been provided in this paper. . An insulator constructed of ceramic and glass is one of the components used in the construction of overhead transmission lines. In the insulator, the material used to create the insulation has excellent insulating properties. However, as a result of the outside environment and atmosphere, the insulation qualities of overhead insulators gradually deteriorate and become severely reduced. Electrical stress, mechanical stress, and environmental stress are the three types of stress that can be applied to insulators in general, according to their function. Polymeric insulators, in addition to ceramic and glass insulators, are also utilized in the building of overhead insulators to keep the electricity flowing.