Water tree, electrical tree and electrochemical tree formed by premature defects of the cable can induce fault. The failure rate of the cable connecter which is higher than cable itself can emerge water tree, electrical tree and electrochemical tree. Meanwhile, the flashover, partial discharge and overheated of the cable joint are also the important reasons for fault. The oscillatory wave of detecting the power cable insulation defects based on is put forward in this paper in terms of the problems existed in the cable detection technology. With the application of oscillatory wave and signal source on the spot, this method dynamically generates reference database of detecting the cable insulation defects, to discriminate the fault patterns correspond to the maximum of function and detect the type, location and severity of cable insulation's defects. Water tree fault of premature cable itself and cable joint can also be detected in this method.