An evaluation method for considering the influence of standby transmission components on the transmission system reliability is presented. Two typical cases for analyzing the standby transmission components are considered. For the cases that the system network structure is not changed by the switching of standby components， a seven-state reliability model considering the switching time of standby components is presented. For the cases that the system network structure is changed by the switching of standby components， the compensation method is used to simulate the influence of the standby components switching on the system grid. Sequential Monte Carlo simulation is used to simulate systems with standby components. The practical calculation example shows that the system reliability is improved to a certain degree， and the average deviation of system reliability indicator， i. e. expected energy not supplied（EENS）， is reduced. While using the method presented， the evaluation results of the system reliability is closer to the actual situation， and the weak links of the system can be found more accurately， thus provide an important reference to the operation and planning of power systems.