Based on photovoltaic (PV) grid-connected micro-inverter an optimized sine-wave control strategy is proposed in this paper and the high efficiency, small volume and low harmonious micro-inverter is achieved. Furthermore harmonic issues under quasi-resonant ZVS mode with flyback inverter and current source grid-connected are analysised in depth to realize grid-connected power generation with high efficiency and high quality energy. Finally, validity and feasibility of the proposed control strategy is proved by experimental results.