In order to solve the problem of three-phase LLCL grid-connected inverter with harmonics at the switching frequency and at the resonance peak of the system under the weak grid, firstly, the comparative analysis of LLCL-type and LCL-type filters as well as the mathematical models when active damping method and passive damping method are respectively used, and then a hybrid damping method combining the active damping method and the passive damping method is proposed, i.e., based on the active damping method, a small resistor is added in series in the capacitive-inductive branch, combining the advantages of the two, to reduce the problem of long control delay of the active damping method without increasing the loss. The MATLAB simulation results show that the hybrid control strategy has a better harmonic suppression capability compared with the active damping method.