Generally, the VSC-UHVDC system is composed of hybrid-MMC with the structure of high and low MMC groups in series. During the on-line entry process of a single MMC, there may be a special start-up charging condition of DC link short-connected. Because of its special charging circuit, a new charging strategy should be proposed for the DC link short-connected condition of the hybrid-MMC. First of all, analyzing the charging circuit when the hybrid-MMC blocking on the special charging condition, and explaining the phenomenon that only the FBSM is charged in the circuit while the HBSM is unable to be charged. Then, proposing a special "cut-off" method of sub-module in order to change the charging circuit. In this way, the voltage of HBSM and FBSM can be charged to the rated value. Finally, the simulation model of VSC-UHVDC is established based on MATLAB platform to verify the above charging strategy. And the simulation results show that the FBSM and HBSM in the hybrid MMC can be charged to the rated value evenly, which verifies the effectiveness of the strategy.