Abstract: Modular multilevel converter-based highvoltage DC transmission（MMC-HVDC） technology has become an ideal solution for grid integration of large and remote offshore wind farms. Due to the characteristics of MMC topology, subsynchronous oscillation（SSO） phenomena might occur due to the interaction between wind farms and MMC-HVDC systems. The SSO of DFIG-based wind farm integration through an MMC-HVDC system was studied. The mechanism of distribution and propagation of the SSO current in the MMC-HVDC system was revealed. A control scheme for SSO current suppression was proposed from the perspective of converter control in the sending-end converter station of the MMC-HVDC system. The detailed model of a two-terminal MMC-HVDC system with 21-level was established by using MATLAB/Simulink. Both the theoretical analysis and control effect of the proposed SSO current mitigation strategy are validated by the simulation results.