Abstract: In order to prevent the DC fault current from threatening the safe and reliable operation of the modular multi-level converter high voltage direct current (MMC-HVDC) grid, this article proposes an active damping current-limiting strategy for the half-bridge MMC DC side faults, restricting the peak and rising rate of the DC short-circuit current and the arm current. Firstly, the influence of the system control strategy on the fault current was studied in this paper. By using the arm current to adjust the differential and common mode modulated waves respectively during the fault period, the number and distribution of the sub-modules in the upper and lower arm were changed so as to achieve the purpose of quickly suppressing both the AC and DC side fault currents. Secondly, the analytical formula of the fault current considering the active damping current-limiting strategy was deduced, and the influence of the current-limiting strategy on the stability of the control system was analyzed, providing a theoretical basis for the selection of the active damping parameters. Finally, the four-terminal DC grid model was built in the PSCAD/EMTDC. The simulation results show that the proposed active damping current limiting strategy is able to significantly reduce the fault current of the DC circuit breaker and ensure the safety of the devices in the arm.