One-degree-freedom and three-degree-freedom internal model control can achieve the decoupling of the active and reactive power. In the one-degree-freedom internal model decoupling control, only a internal model control is used to regulate the output tracking、robustness、anti-interference of the system, making the decoupling and dynamic performance of system limited. In order to overcome the shortcomings, three-degree-freedom internal model decoupling control method used in VSC-HVDC is presented in this paper. The feedback controller is applied to regulate the robustness, the feed-forward and given internal model controllers are respectively applied to regulate the anti-interference and output tracking. A HVDC system of three terminals is built and simulated in PSCAD/EMTDC. The results validate that three-degree-freedom internal model decoupling control have a better output tracking、robustness and anti-interference than that of one-degree-freedom internal model decoupling control.