The application of half bridge modular multilevel converter (MMC) in DC deicing system has the advantages of low harmonic content, small volume, high economy and reactive power support. In order to meet the ice melting requirements of lines with different lengths and resistivities, a half bridge MMC ice melting system with Buck chopper unit and its cooperative control strategy are proposed to realize the wide range continuous adjustment of DC voltage. Aiming at the different deicing current requirements of DC side, an active control method of MMC bridge arm voltage is proposed to realize the adaptive adjustment of DC outlet voltage. Considering the requirements of AC outlet voltage and the constraint of maximum modulation ratio, the coordination scheme of MMC bridge arm voltage and DC side additional Buck chopper circuit is designed. The wide range of deicing line voltage is realized by controlling the duty cycle of Buck chopper circuit regulation in order to meet the ice melting needs of different lines at the same time to ensure the power quality of the AC side. Finally, a simulation model is built in MATLAB/Simulink to verify the correctness and effectiveness of the proposed cooperative control strategy.