For avoiding the oscillation instability risk caused by MMC(Modular Multi-level Converter), the AC- and DC-side disturbance characteristics of MMC is deeply researched. Firstly, based on the dynamic characteristics of bridge-arm inductor and sub-module capacitor, the state-space model of MMC is established. Specially, the influence of the DC-side mid-point voltage is considered. Moreover, based on the frequency component balance principle, the frequency components of each variable in MMC under normal situa-tion, AC- and DC-side disturbance situations are analyzed. Meanwhile, the multi-frequency disturbance matrix is derived to describe the relationship among disturbance frequency components of each variable. On the basis, the accuracy of multi-frequency disturbance matrix is verified by time-domain simulation, and the AC- and DC-side port-impedances of MMC are calculated in sub- and super-synchronous frequency range. Finally, the disturbance amplification effect of MMC is further analyzed based on impedance-frequency characteristics. The results indicate that MMC will amplify the disturbance of certain frequencies in sub- and super-synchronous frequency range, and the specific frequency is related to the system parameters. © 2020, Electric Power Automation Equipment Press. All right reserved.