The invention provides a three-phase grid-connected MMC static model for direct-current voltage control characteristics and a building method. An equivalent model in a dq rotating coordinate system ofa grid-connected MMC is provided, on this basis, the static characteristics of the MMC is analyzed, the output direct-current voltage gain characteristics of the MMC under the different parameters and the amplitude modulation ratio are analyzed, it is indicated that the MMC has the working modes of inductance leading and capacitance leading which can be stable in change in the full range of the amplitude modulation ratio, and between the two modes, a system voltage gain equation has a pole; the input power characteristics of the MMC are researched, the working range under the system direct-current voltage in the inductance leading mode and the capacitance leading mode is analyzed, and it is proved that for the grid-connected MMC, under certain condition, the feasibility of the low direct-current voltage pressure is achieved. The three-phase grid-connected MMC static model is used for analyzing the physical characteristics of the three-phase grid-connected MMC in the steady state, themodel is simplified through system differential equation combination and matrix transformation, and the groundwork is laid for control over the grid-connected MMC.