Some rail transit system in China adopts the power frequency single-phase AC system to improve the running speed and transportation capacity of trains. When the traction power supply system fails, the one-side power outage emergency repair scheme may be adopted. If the induction voltage on the catenary is too high, it will cause harm to maintenance personnel. In this paper, a simulation model of subway tunnel was built based on the design data of a subway. The induced voltage on the overhead catenary line is obtained When it is cut off for maintenance, and the other side of the line is in normal operation. Influences of the traction current, the distance between the tunnels and other factors on the induced voltage are also gotten. It is found that the inductive voltage on the overhead catenary line will exceed the safety level when the single-ended grounding mode is adopted. If the double-ended grounding mode is adopted, it will be reduced below the safety limit. According to the above research results, proposes were given in this paper that when the subway unilateral power outage maintenance operation is adopted in the AC power supply system, the both ends of the maintenance interval must be grounded. The conclusion of this paper can be used as a reference for the subway management department to formulate safety measures.