Long March 5 (LM-5) is a new generation of heavy-lift launch vehicle developed by China. It has successfully completed the first Mars exploration of China and the 3rd phase of China lunar exploration program of Chang’E 5 (CE-5). LM-5 experienced 30 years of key technology research and engineering development. During this period, a lot of engineering technical problems were conquered, rich experience in the development of large cryogenic launch vehicle was accumulated, and the development of the new generation launch vehicle system was constructed. The research capability and foundation of carrier rockets have been greatly improved. This paper describes the development background of LM-5. Based on the overall rocket technical scheme and technical innovation, this paper discusses the development thinking of the rocket, the modular configuration scheme, the overall optimization design technology of the whole rocket and the structure technology of the large diameter and large concentrated load rocket body, and probes into the key technical problems of the LM-5 for the deep space exploration mission, specifically, the orbit design and optimization technology for deep space exploration mission, and narrow window multi-orbit launch technology. LM-5 is a landmark project of China’s new generation of launch vehicle, representing the highest level of launch vehicle technology of China, and is a significant symbol for China’s transformation from a major player in space to major power in space.