Abstract: Helical coil once-through tube steam generator (HCOTSG) is a common form of steam generator. Due to its unique advantages, helical coil once-through tube steam generators are widely used in various reactor power systems. In this paper, a CFD computing method for coupling the flow and heat transfer calculation of liquid lead-bismuth in the shell side and two-phase fluid in the pipe wall of liquid metal HCOTSG was proposed by using the software FLUENT. The numerical simulation method was compared with relevant experimental research and the correctness of the numerical simulation method was verified. On this basis, the liquid metal HCOTSG under typical working conditions was numerically simulated. The distribution of thermal-hydraulics parameter inside the steam generator was obtained and the flow and heat transfer characteristics were analyzed. This study provides a new way for the study of flow and heat transfer characteristics and structural design optimization of liquid metal HCOTSG.