The problem of overheating fault of high-voltage isolation switch has brought unavoidable safety hazard for power system.The temperature rise is an important index to evaluate the operation state of isolation switch.The contact resistance value is the key parameter to indicate whether the connection of the conducting circuit is good.The temperature rise of the isolator is mainly controlled by the contact resistance.When the contact resistance changes,the overall temperature distribution of the isolation switch changes.In this paper,the effects of different defects of the contact resistance and the maximum temperature rise on the contacts of GW6B-252 isolation switch are studied.The conclusion is occurred that the contact pressure of the GW6B-252 should be above 400 N,and the fouling of the contact has the greatest influence on the temperature rise of the GW6B-252 isolation switch.