This study investigates the formation feasibility of the integrated bottom car body components with dual die casting injection molding technology. During the production of a die-cast super-large one-piece body part weighing over 10,000 t, a thorough comparison and investigation were conducted on the arising issues, using both single and double injection systems. Particular attention was given to meticulously discussing the die casting filling problems and microstructural defects that originated from the filling process. The research findings indicate that the implementation of a double injection system can significantly minimize cold shuts and reduce the solidification time. The effectiveness of this die casting technique was further confirmed by the production of high-quality castings using a scaled model that replicated real casting conditions at a 1:3 ratio, thereby maintaining a one-to-one correspondence in essential aspects. This successful study offers both theoretical insights and practical applications for the production of integrated bottom car bodies utilizing die casting in conjunction with a dual injection system.