Abstract: Using related equipments of Qinshan Nuclear Power Plant as prototypes and based on the steam generator model and the optimization calculation code developed before, the thermal-hydraulic system code of RELAP5 was used to verify the accuracy of the steam generator model. Both the steady state and the power load increase transient behaviors of the optimized steam generator were studied by code simulation. The results show that the mathematical model developed for the steam generator is applicable. Under the overload operation condition, the problem of low circulation ratio may occur in the optimized steam generator design. The results also indicate that RELAP5 can be used as a validation code for optimizing the design scheme of nuclear power equipment.