This paper proposes a HERIC based transformerless inverter for grid connected PV system. The proposed circuit consists of a symmetrical boost chopper and a HERIC inverter. The common mode voltage, therefore, is always kept at a constant value, and hence the proposed circuit can reduce the leakage current. Furthermore, a partial sinewave tracking dual mode control is adopted. The symmetrical boost chopper operates only when a boost operation is required. Compared to the conventional PV inverter, which always operates the boost chopper at high frequency, the proposed circuit reduces the switching loss. This paper shows the operation principle, theoretical equations for common mode voltage, and the experimental results.