Abstract: The transient stability of multi-machine power system with static var compensator(SVC) is proposed. First, the multi-machine power system model with SVC is established. Then, based on the concept of equivalent load, the energy function of the power system with SVC is proposed. And it is verified for the monotonic decreasing property of the energy function after fault-clearing. The potential energy due to SVC is expressed by the voltage of the grid-connection point and the power injected into it, which overcomes the difficulty brought by the complicate structure of SVC. Using the proposed energy function, the transient stability is analyzed by the PEBS method. The iterative potential energy boundary surface method(IPEBS) is validated on a modified 3-machine 9-nodes system and 10-machine 39-nodes system. Compared with the time domain simulation, the calculation results show that the error of the critical clearing time(CCT) is down.