A modularized multi-level current converter asymmetric double sub-module midpoint electric potential equalization control method. In an MMC formed by asymmetric double sub-modules and half-bridge sub-modules, each phase is formed by an upper bridge arm and a lower bridge arm, and each of the upper bridge arm and the lower bridge arm is formed by connecting i half-bridge sub-modules and N-i asymmetric double sub-modules in series; each half-bridge sub-module comprises two IGBTs, two diodes and one capacitor; each asymmetric double sub-module comprises four IGBTs, four diodes and two capacitors; when a fault occurs on a direct current side of MMC, all IGBTs are locked, capacitor voltage is used for forcing switched-on diodes to cut off and block a fault current in a reverse direction, asymmetric double sub-module midpoint electric potential equalization control is adopted, asymmetric double sub-module midpoint electric potential equalization of MMC comprising the asymmetric double sub-modules and the half-bridge sub-module is maintained, and operational reliability and security of MMC based on the asymmetric double sub-modules and the half-bridge sub-modules can be improved.