Abstract: In view of the problem of common-mode current existed in topology of single-phase transformerless type photovoltaic grid-connected inverter, several topologies were introduced which can restrain common-mode current effectively, namely single-phase full-bridge topology with double-polarity modulation, full-bridge topology with AC bypass, H5 topology and NPC topology. Principle of restraining common-mode current of these topologies were analyzed in details, and these topologies were compared in terms of switching loss and system efficiency. Finally, it was pointed out that H5 topology has best performance.