The full-bridge inverter with hybrid PWM (HPWM) has higher efficiency and lower filtering requirement. However, when it is used for grid-connected transformerless photovoltaic system, the ground current may be high due to the parasitic capacitors and high frequency common-mode voltage. In this paper, the single-phase three-leg inverter is proposed to suppress the ground current. The additional leg is parallelled with the full-bridge inverter. The analytical method is established to calculate the ground current. The common mode voltage of the inverter can be reduced to suppress the ground current. Finally, the validity of the proposed method is verified by simulation results.