This paper based on PSCAD electromagnetic simulation software,and study the Yidu-Huaxin HVDC transmission engineering in-depth. Using the actual data of this project,the detailed models of the primary system including AC system,converter transformer, AC/DC filter and other components are built.The control system model in the secondary side is referring to CIGRE model. This paper introduced the principle of the control system in detail.Based on the primary system model and the secondary system model,the model of Yidu-Huaxin HVDC system is built up,and perform simulation in both normal and fault conditions.The simulation result verifies the stability of the model and the model can accurately simulate the Yidu-Huaxin HVDC system,so it can be used as a platform for further research on Yidu-Huaxin HVDC system.