Abstract: To study the cavitation characteristics of the reactor coolant pump, the existing Zwart-Gerber-Belamri thermodynamic cavitation model has been improved by considering the heat transfer effect correction based on ANSYS CFX software, and the reactor coolant pump model is simulated before and after the improvement of cavitation model at different flow. Then, the comparative analysis of simulation and experimental values is verified that the thermodynamic effect improvement is correct when the reactor coolant pump cavitation occurs. The results show that when the cavitation does not occur, the improved model does not have an significant influence and the influence increases with the development of reactor coolant pump cavitation. Numerical simulation predicted trend of the model pump cavitation performance is consistent with the experimental values and the error value is in the 5.3% to 9.6%, which verified the numerical simulation of cavitation performance has a reliable prediction for engineering applications of reactor coolant pump. With the decreasing of NPSH, the area of low pressure expan from import to export on the impeller blade and bubble fills the entire impeller passage, also the head reduced.