Abstract: Distribution network is an important component of power system. Changing straight pole to tension pole can achieve precise maintenance of distribution lines, which is one of the common works. During the process of tightening or disconnecting the line, the operators do not use line backup protection or use insulated ropes as simple backup protection, which will pose significant safety hazards, high levels of risk, and inconvenient and inefficient operation. Therefore, a line backup protection device for live-line work is designed, which has a simple structure, high mechanical strength. The length of the insulation rope can be adjusted timely to avoid manual adjustment by operators, so the safety and work efficiency of operators is further improved.