Two-stage grid-tied single-phase inverters with a Boost stage and an H-bridge stage are potential for PV generation system with simple structure, high extensibility and wide Maximum Power Point Tracking (MPPT) range. Besides, the two stages can be optimized individually to achieve the best performance. However, applying unipolar modulation on the H-bridge may introduce large leakage current so bipolar modulation had to be chosen, resulting in large magnetic hysteresis loss and switching loss. To reduce these losses, a hybrid modulation method combining both bipolar and unipolar modulation is proposed in this paper, and by cooperating with the Boost stage, the leakage current can be well suppressed with the proposed modulation method. The design consideration of the proposed method is presented and verified by experimental results from a 1kW prototype.