According to the current Guide on Security and Stablility for Power System, the reclosing moment of power plant transmission lines directly affects the power plant transmission ability. This paper establishes a mathematical model of system transient stability affected by reclosing moment. The system stability characteristics considering reclosing time is studied based on Extended Equl-Area Criterion (EEAC) theory. An approach to setting the reclosing time considering transient stability is proposed. The actual power system simulation shows that it can identify the reasonable range of reclosing time quickly and ensure that the setting value of reclosing time meets the system transient stability requirement.