For an optimal performance of a modular multilevel converter (MMC), a tradeoff between multiple objectives can be complex. The injection of zero sequence voltage and circulating current can enlarge modulation index and to diminish the submodule capacitor voltage fluctuation. In this paper, a multi-objective genetic optimization algorithm is proposed to improve the performance of MMC in minimizing both the capacitor voltage ripple and current stress. The amplitude and phases of the circulating current and zero sequence voltage are designed in optimal coordination. Simulation in MATLAB/Simulink is implemented to validate the effectiveness and feasibility of the proposed method.