The resonance of a multi inverter grid-connected system will threaten the stable operation of a power grid. Because of its good filtering effect, an LCL filter is often used as the output filter of a grid-connected inverter. In recent years, many resonance mechanism analysis and suppression methods of the LCL multi inverter grid-connected system have been proposed, and analysis and summarizing are needed. First, the circuit topology and equivalent circuit of a multi inverter grid-connected power generation system are introduced. Second, the basic concepts of the frequency domain analysis, modal analysis and multi input multi output model analysis methods, and their new achievements in the analysis of system resonance mechanism are explored. Then, the advantages and limitations of active damping and impedance reshaped methods and an active damper in system resonance suppression are emphasized. It is revealed that the application of virtual resistance and a notch filter is the key technology of the above methods. Also the applications of hierarchical control, controller parameter optimization and system configuration optimization in system resonance suppression are also analyzed. Finally, from the perspective of the construction trend of the new type power system, the development of a multi inverter grid-connected system towards complex systems with large-scale, multi parameter and different control methods is considered. It needs a combination of multiple analysis methods to accurately analyze the resonance mechanism. For the suppression methods of multi inverter grid connected resonance, the traditional active damping and impedance reshaped methods and the active damper will be further studied, and on-line resonance monitoring technology may become a new breakthrough in this research. This work is supported by the Key Research and Development Program of Sichuan Science and Technology Department (No. 2022YFG0117).