In order to resolve the leakage current problem, this paper proposes a new finite-set model predictive control to reduce common-mode voltage of three-phase inverter. The model of photovoltaic (PV) grid power generation systems is analyzed. The study finds that only the nonzero vector is used to reduce the common mode voltage. Therefore, the nonzero vector is brought into the value function and the optimal vector is got to be used in the next cycle. The common-mode voltage can be limited to ±1/6Vdc by using the proposed finite-set model predictive control. This method can suppress the leakage current and guarantee the safety of human life. Compared with traditional PI method, it can improve the current tracking speed and precision. Therefore, the proposed model predictive control can reduce the common mode voltage and load current and has fast dynamic response.