The screen chemicalpotential ( E s) and the sheath insulating resistence ( R s) can effect the detected data in most on line detecting method for XLPE cable, especialy, to the “DC method”. The key to eliminates or reduces the disturbance is firstly to monitor the data of E s and R s in time. In this paper, by analyzing circuit and simulating test, the author has developed a simple and reliable on line test method for examining the data of E s and R s of XLPE Cable.