The high-frequency oscillation problem of MMC-HVDC (modular multilevel converter high voltage direct current) is mainly due to the negative damping characteristic caused by MMC’s control link delay. Passive damping scheme is an important way to suppress the high-frequency oscillation when the active damping scheme cannot avoid the negative damping characteristic of MMC. Based on the high-frequency impedance characteristic of MMC and the system oscillation mechanism, this paper analyzes the positive damping criterion for passive damping filter parameter design, and a set of passive damping filter parameter design method is proposed. Finally, the effectiveness of the proposed passive damping filter design method is verified by simulation.