In order to quantitatively evaluate the influence of UPFC device on the operation reliability of power grid,this paper takes UPFC project of 200 kV Nanjing West Ring Network as the example,and the method and process of the reliability evaluation of the system with UPFC is analyzed.First,based on UPFC subsystem division,the reliability model of each subsystem with no spare components and spare components is established.Based on this,the two-state model of UPFC system is obtained.Finally,combined with the case of Nanjing West Ring Network,it was mainly analyzed the influence of different schemes such as UPFC,new line and double capacity wires and different installation locations of UPFC on the reliability of power grid.