Abstract: The turbine model which can represent accurately non-isentropic process in the stage of turbine and system dynamic characteristics was developed and added into RELAP5 code, and the improvement of the turbine model of RELAP5 was implemented. The improved turbine model is based on the characteristics of steam flow and work transfer in the stage of turbine and considers adequately the impact of internal configuration parameters and oblique shock which is developed by non-equilibrium condensation of wet steam in turbine. Through building internal coupling interface and the modifying input processing subroutines, turbine model was developed as a part of RELAP5 hydrodynamic model. Taking the turbine of Qinshan 300 MW Nuclear Power Plant as an example, the simulation calculation and comparative analysis were performed for both stead and dynamic cases respectively by both the original and the modified turbine models in RELAP5 code. The results show that the modified turbine model can represent more accurately the dynamic operation characteristics of the turbine.