There are many 500 kV tranmission lines running in high altitude area below 2000 metres above sea level，which has accumulated rich experiences in design，operation and maintenance． However，in the areas over 2000 metres above sea level， there is a lack of experiences in insulation configuration and running data of 500 kV AC transmission lines． With the planning and development of hydropower resources in Lancang river，Nujiang river and Yarlung Zangbo river basin，and the planning and construction of backbone power grid in Tibet or western Sichua，many 500 kV transmission lines will be constructed in high altitude area above 2000 metres above sea level． According to the experiment results of artificial pollution flashover performance executed in low atmospheric pressure under imitated condition of high altitude by State Grid Electric Power Ｒesearch Institute，the creepage distance method and the pollution withstand voltage method are compared which are often used to choose the insulators under pollution condition，and the pollution flashover performance of double － shed，triple － shed and anti － fog insulators are also compared． The influence of low atmospheric pressure on the pollution flashover performance of insulators and the altitude correction methods for flashover performance contaminative insulator are discussed，and the insulation configurations for 500 kV AC transmission line in high altitude areas are recommended．