In this paper, a photovoltaic (PV) gird-connected micro-inverter controlled by power factor correction (PFC) controller is implemented. The PFC controller is adopted to control the inverter output current sinusoidally. Besides, the maximum power point tracking control circuit can get the maximum power form PV modules. The duality between the PFC circuit and the inverter circuit is presented first. Then, the PFC design rules is applied in the inverter circuit. However, the flyback inverter controlled by boundary conduction mode (BCM) PFC IC will cause a high third harmonic component from the analysis. Hence, the third harmonic injection method is estimated and analyzed to improve the output current total harmonic distortion. Finally, a 300W grid-connected flyback micro-inverter with BCM control based on L6561 PFC controller is implemented to verify the feasibility. Input voltage is 20V to 40V and the peak power is 300 W from PV simulator, and the output voltage is 220Vac/60Hz. The highest efficiency of the micro-inverter is 92.8%.