Background: The coolant flow and heat transfer in the reactor are significant to the safety of pressure water reactor (PWR). Purpose: This study aims to obtain the coolant flow and heat transfer characteristics in the reactor core. Methods: The complete model of pressure vessel is built by Pro/E

and the thermal hydraulic characteristics of the core are simulated with commercial software CFX by using the porous medium model in the core. Results: The simulation results show that the application of porous media model can display the core coolant temperature distribution effectively and correctly

and the asymmetric operation conditions can cause asymmetric on reactor core. The transient accident calculation results show that the highest temperature of the coolant appears in the upper of the core. Conclusion: The porous media model can be used in the reactor core and it has a certain reference value for the thermal-hydraulic safety of pressurized water reactor.Cited