In order to solve the power supply problem of AC/DC hybrid system, an expansion planning model of AC/DC hybrid power grid with Voltage Source Converter (VSC) is proposed. Firstly, the steady-state model and typical control strategies of VSC components are analyzed. On this basis, the AC and DC power flow calculation method with VSC is studied. Then, aiming at minimizing the cost of generation operation and maintenance, an optimization model for expansion planning of AC/DC hybrid power system is proposed. The feasibility and effectiveness of the model method are verified by the examples, and the whole process of calculation is shown. In addition, the results also show that different VSC component control strategies will affect the power flow, and then affect the final expansion planning results. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGSCJY00GHJS1800026).