Abstract: Three dimensional numerical simulations and flow analysis were carried out to study the resistance and flow field of the steam flow limiter adopted in a steam generator. The realizable k-ε model with standard wall function was utilized to calculate the three-dimensional flow field of the flow limiter. The effect of the structure on the flow details and resistance was studied through analyzing the simulation results. The resistance of the flow limiter increases with the inlet mass flow rate while the resistance coefficient maintains constant, about 4.95 and 3.05 respectively. For the 7-nozzle flow limiter, the major pressure loss, about 71.4%, is caused by the backflow region, while for the 19-nozzle flow limiter, the major pressure loss is caused by the Venturi nozzles and the backflow region, about 50.5% and 44.5% respectively. The pressure, velocity and turbulent kinetic energy in the flow fields of the 19-nozzle flow limiter reach steady more rapidly than that of the 7-nozzle flow limiter. For the 7-nozzle flow limiter, the mass flow rate of the centric nozzle is 1.04 times that of the outer nozzle, while for the 19-nozzle flow limiter, the mass flow rate of the centric nozzle is 1.18 times that of the outer nozzle. The outer nozzle of the 19-nozzle flow limiter has backflow region in its diffuser, hence the performance of the 19-nozzle flow limiter could be improved through optimizing its structure.