Abstract: In this study the main equipments and the primary loop of PWR nuclear power plant (NPP) were analyzed in detail. The model of point neutron dynamics, steam generator model with two phase drift flux governing equations, 3-zone non-equilibrium pressurizer model and 4-quadrant main pump performance model were established. Based on the above models, a NPP simulation program was developed by using mixed programming with FORTRAN90 and Visual C++. The simulation program is of capability to achieve visualized simulation for the main equipments in primary loop and entire system of PWR nuclear power plant. It provides not only the visualized functions of real-time plotting, zooming, etc., but also the output of numerical results with standard picture and/or text formatting files. Besides, the program was validated by comparing the calculation results of the program developed by authors and those of RELAP5/MOD3.0.