In order to make two-stage single-phase photovoltaic grid-connected inverter system have high conversion efficiency while possessing the ability of alleviating leakage current, the paper proposes a novel high efficiency two-stage single-phase photovoltaic grid-connected inverter system which contains ZVS Boost converter at the pre-stage and H6 inverter topology structure at the last stage. The paper analyses their operation principles and studies the overall control strategy of the photovoltaic grid-connected inverter system. Finally, the experimental prototype of the two-stage single-phase photovoltaic grid-connected inverter system is built to confirm the theoretical analysis. The results indicate that this photovoltaic grid-connected inverter system has high quality of grid-connected waveforms and high conversion efficiency. Its efficiency ratio is up to 97.26%.