The multi-functional grid-connected inverter not only realizes the grid-connection of distributed energy sources,but also improves the power quality.With higher performance-price ratio,it lowers the system cost and size,more suitable for the microgrid and distributed generation system.Its topologies are overviewed from the aspects of single-phase and three-phase systems,and compared and evaluated in view of system parameter,capacity,switching frequency,auxiliary function,application,etc.The novel topologies,advanced control strategies,soft switching technique,large power applications,integrated power-electronic system stability,etc.are considered as its possible future research fields.