Abstract: Residual stress of a high strength insulator cylinder machined by three kinds of methods including diamond-blade incising,diamond-wheel grinding and whetstone polishing was analyzed by using X-ray diffraction.The results show that the residual stress on the insulator cylinder surface was relatively small after machining and was tensile stress.The maximal residual stress generated during the grinding,and the polishing could decrease the stress effectively.The residual stress on the insulator cylinder surface after machining could reach 30%-50% of the rupture strength,which would result in crack,brokenedge or nick on the insulator cylinder surface.