The harmonic coupling matrix model can provide effective support for the study of harmonic stability of power system lines and components. However, for the modular multilevel converter (MMC) with complex internal structure, the matrix model in the existing research can not describe the coupling relationship between harmonics or only discuss the coupling relationship of specific harmonics. Therefore, considering MMC switch function can describe the coupling relationship between specific harmonics of converter, but it is periodic time-varying in itself, and the advantage that HSS can stabilize the periodic time-varying model and describe the coupling relationship between all times of har-monics of various quantities at the same time, the combination of the two can build all times of harmonics that can describe all electric quantities of AC and DC sides of MMC at the same time Harmonic coupling matrix model of wave coupling relationship. Finally, the theoretical calculation results of MMC harmonic coupling matrix model with harmonic disturbance are compared with the simulation results of PSCAD electromagnetic simulation model, which proves the accuracy of the model in describing MMC harmonic coupling characteristics.