Abstract: The UHV DC tension insulator strings are often large-tonnage suspension porcelain or glass insulators with high mechanical strength. The single insulator is heavy, so it is difficult for one worker to make a replacement in live working conditions, and two workers working at the same time are required to make a replacement on insulator strings in live working conditions. The key problem to ensure the safety of double live working is to select the appropriate way to reach the working position to realize the potential transfer between the two workers. In this paper, the combined gap test of ±1100kV tension string live working by two workers is carried out, and the minimum approach distance required for live working by two workers of ±1100kV transmission line tension string is calculated and obtained. The electric field calculation model of live working of ±1100kV tension tower tension strings by two workers is established. The process that two workers enter and leave the working position along the tension string and different conditions that two workers replace insulators are simulated and analyzed, and distribution characteristics of the electric field of insulator strings and live workers are obtained. According to the calculation results, when the two workers replace the tension insulators in different tension strings, it is easy to realize the potential transfer, so as to reach the same potential for work. The results of this paper provide a theoretical basis for ±1100kV UHV DC live working of insulator replacement by two workers.