Aiming at the lightweight demand of modular multilevel converter (MMC), an arm multiplexing modular multilevel converter (AM-MMC) with high utilization of sub-modules is proposed. According to the characteristics of AM-MMC topology, the modulation signal is divided into three groups and input into different arms. A splitting modulation strategy is designed to meet its modulation requirements in the field of HVDC transmission. The simulation results based on Matlab/Simulink show that under the proposed strategy, AM-MMC can successfully complete the AC/DC voltage conversion and energy transmission, and the operation effect is good, and the voltage of the three sub-modules is stable at the rated voltage fluctuation under the split modulation strategy.