Abstract: In order to study heat transfer and mass flow of primary loop of nuclear power plant, under the specific operating conditions, a scaling method of Ishii was applied to simulate essential systems of primary loop of PWR, and main parameters of experimental loop coupling with pump and interconnected systems were obtained. Then, mechanistic analysis code package was applied to analyze the experimental loop. The results show that main designed parameters of experimental loop based on the scaling method of Ishii are reasonable and feasible, and the interaction of heat transfer and mass flow of primary loop systems of prototype, under the transient conditions, can be studied.