Abstract: The station controller is the core of flexible HVDC control system for modular multilevel converter (MMC), which is coordinated with the host computer and lower controller to realize the reliable control of flexible HVDC transmission. In this paper, the main function of station controller based on MMC-HVDC is analyzed, and the hardware architecture design scheme of station controller is proposed. In addition, the software program logic is designed according to the hardware scheme and functional requirement. Furthermore, a 4kV/100kW MMC-HVDC experimental prototype based on the designed station controller is developed, on which several stability and voltage experiments are carried out. The results show that the system can quickly regulate active and reactive physical quantities, and protect system from AC system fault and controller communication fault, which verify the correctness of the designed hardware configuration and program logic of station controller.