The invention discloses an MMC submodule capacitor voltage balancing control method based on quick sorting. The method comprises the steps that a submodule capacitor voltage value in a removal state and a submodule capacitor voltage value in an input state are stored in a definition array A[xn-1] and a definition array B[ym-1] respectively; first-round sorting is only conducted on the A[xn-1] or the B[ym-1] according to the different conditions to obtain corresponding low voltage arrays and high voltage arrays; second-round sorting is only conducted on the A[xn-1] low voltage array or the A[xn-1] high voltage array or the B[ym-1] high voltage array according to the further condition to obtain some segmentation arrays; after second-round sorting, deltaN submodules in the corresponding segmentation array are selected to be input or removed in sorted list according to specific instructions. According to the method, balancing control is conducted on the MMC submodule capacitor voltage by adopting a divide and conquer strategy idea on the basis of a quick sorting algorithm, not all the submodules of a bridge arm are completely sorted, the traditional sorting and calculating time is shortened, and the calculation speed of an MMC bridge arm submodule capacitor voltage balancing algorithm can be more effectively increased.