Withstanding characteristics of several typical control cables under 50Hz AC, DC and lightning impulse overvoltage are tested and studied, results show that surface discharge voltage of cable terminal tends to saturate with the increase of pole distance; it have great effect on the withstanding characteristic of control cables that head and shield of its are treated well or not; the insulating property between shield and core wires is the most unsubstantial link in the whole insulation of control cables, it can withstand more than 18kV 50Hz AC voltage, 45kV positive DC voltage and 40kV negative lightning impulse voltage in 30 seconds. The grounding potential rise of grounding network should be controlled under their tolerance range in actual project.