For a hybrid converter composed of full bridge sub-modules and half bridge sub-modules, the possible problem of half bridge sub-modules being unable to equalize voltage during voltage reduction operation is analyzed, and a control strategy for voltage reduction of the hybrid converter is proposed. Firstly, a mathematical model of the bridge arm current of the hybrid converter is established and its characteristics are analyzed. In response to the possibility that the bridge arm current of a hybrid converter may only be positive or negative during voltage reduction operation, a control strategy of reactive power compensation is proposed to achieve positive and negative bridge arm current by utilizing the flexible reactive power control characteristics of the modular multilevel converter （MMC). Finally, a hybrid converter model of voltage source converter-high voltage direct current （VSC-HVDC) is established in PSCAD/EMTDC. The simulation results show that the proposed control strategy can meet the voltage equalization requirements of the sub-modules under the condition of significant voltage reduction operation in the DC system, avoiding the situation where the sub-modules cannot be equalized during the DC voltage reduction operation.