For a grid-connected inverter based on an LLCL filter, a hybrid damping control method combining active and passive damping methods can well suppress the harmonic at the resonance peak and switching frequency of the system. First, the characteristics of passive and active damping methods of an LLCL filter and the effects of two methods on the gain at resonant peak and switching frequency of the system are analyzed. Secondly, the design method of hybrid damping parameters of LLCL filter is obtained by comparing the two methods. Finally, through simulation and experiment with a three-phase grid-connected inverter, the hybrid damping parameter design method and proposed control strategy are verified. This work is supported by National Key Research and Development Program of China (No. 2018YFB0105700) and Plan of Applied Basic Research Programs of Wuhan (No. 2017010201010116).