Abstract: Most of the power line faults are caused by insulation problems. And the current way to deal with insulation failures is passive overhaul after the accident. So the insulation fault early warning system of power line based on traveling wave technology was developed. It could eliminate the insulation fault in the early stage of fault. based on the insulation fault early warning principle, the insulation fault early warning system of the power line was designed. and the field test was carried out.The field tests results showed that the insulation fault early warning system of the power line can give early warning of insulator partial discharge with high sensitivity and precision of fault location is high with an average error 0f 70 meters, which can meet the requirements of field operation.