Unbalanced load increases imbalance and harmonic distortion of system operating voltage, which results in the influence of power quality in micro-grid. Sliding-mode variable structure control is proved to be robust and has plenty of remarkable dynamic response characteristics, so that it could be applied to the micro-grid operation with unbalanced load control. The mathematical model of the system is established, and an appropriate control strategy is designed to achieve a smooth mode-switch among diverse micro-grid operating modes. The experimental results of PSCAD/EMTDC show the feasibility and effectiveness of the proposed approach.