The invention belongs to the technical field of electrical power system model simulation and control and especially relates to a modular multilevel converter capacitor voltage balance control method based on classification. The method is characterized by carrying out classification on all capacitors in a bridge arm through submodule capacitor voltage rated fluctuation range, and summarizing the number of the capacitors included in each class; carrying out priority ranking on the classes according to the direction of the current in the bridge arm; determining ranking class according to the number of the capacitors needing to be input and the ranking sequence; and inputting all the capacitors in the class prior to the ranking class, and selecting residue number of capacitors needing to be input in the ranking class and inputting the capacitors. The method reduces switching frequency of a switch device and calculation quantity of the control method under the condition of guaranteeing the capacitor voltage fluctuation range, and the response speed of a control system is improved.