This review paper provides a comprehensive analysis of transformerless grid-connected inverters, focusing on their operational principles, key topologies, benefits, challenges, and potential future developments. Traditional photovoltaic grid connected inverter usually has power frequency transformer or high frequency transformer, which brings many inconvenience. Due to the existence of equivalent parasitic capacitance of photovoltaic cell board to ground, it will lead to the generation of ground drain. Provided are a non-isolated photovoltaic grid-connected inverter and a control method therefor. However, the disadvantages of isolation transformers, such as large volume, high cost, and low efficiency, cannot be ignored.