Abstract: Earthquakes can have devastating effects on power grid． At present，the approximate analysis of seismic performance is the main method to evaluate the reliability of power grid under seismic condition，but the approximate analysis results can not meet the actual needs． So，the reliability of transmission towers and the propagation of earthquakes are considered in the reliability evaluation of power grids under seismic condition． The finite element simulation method is used to directly analyze the structural problems of the tower． The reliability of transmission line is calculated by using the tower reliability． After obtaining the reliability data，the reliability of power system under each seismic strength is evaluated． Finally，the propagation of earthquake is considered． The overall reliability of power system is evaluated． The reliability evaluation results of grid reliability under seismic condition can be used to identify the vulnerable links of power system and provide a reference for improving the seismic performance of power system．