Abstract: As a direct AC/AC converter, the hexagonal modular multilevel converter (H-MMC) has broad application prospects in the field of medium-voltage and high-power motor drive. However, due to a large number of H-MMC submodules, how to charge the submodule capacitor to its rated value has become a critical issue to be solved. In this paper, a closed-loop pre-charging control strategy is proposed by studying the topological characteristics and charging loop of H-MMC. The reference of the grid current is calculated based on the set charging power. And the reference of the bridge arm current is derived based on the mathematical model of H-MMC. Quasi-PR control is employed to track the bridge arm current, so as to realize the constant current charging of H-MMC. At the same time, the consistency of the submodule capacitor voltage is ensured by the equalization control. The comparative simulation results of pre-charging based on Matlab/Simulink show that the proposed strategy has controllable charging time, no inrush current and good consistency. Finally, the feasibility of the proposed closed-loop pre-charging control strategy is verified by a small H-MMC prototype.