Abstract: The overall key technical research of the Long March 5 launch vehicle is introduced, such as the optimization design of large low temperature launch vehicle aerodynamic shape, attitude control design of swing booster engine, and large strap-on launch vehicle force and thermal environment analysis method, etc. The overall optimization technology scheme is advanced. New design and simulation technology are adopted and verified through the large ground test. Long March 5 achieves the 14-ton carrying capacity of GTO, and the overall technology reaches the international advanced level of similar launch vehicles. To meet the needs of deep space exploration missions, the overall technical research level of Long March 5 has been optimized and improved.