Abstract: The Steam Generator(SG) is an important connecting equipment between the primary and secondary loop of PWR nuclear power plant. The reliability of the Steam Generator Water Level Control System(SGWLCS) directly affects the safety and power generation efficiency of nuclear power plant. Based on the system structure and control logic of the steam generator water level control system, this paper adopts the Dynamic Fault Tree(DFT) method to model the reliability of SGWLCS. The fault tree model includes dynamic part and static part. The homogeneous Markov chain is used to calculate the hot standby dynamic gate about the control module of the processor and the feedwater valve, and then the whole fault tree model is analyzed according to the logical relationship. Finally, the reliability analysis results of the system and the importance analysis results of the equipment are obtained. The reliability analysis shows that the use of hot spare parts can effectively improve the reliability of the system, and the results of importance analysis can improve the design of the system and give suggestions for regular maintenance of the equipment.