Although mold designs are used in various sectors, molding composite materials results in issues such as deformation and insufficient stiffness. To this end, the response surface method was used to optimize the design of the mold support structure partition, improving the performance parameters of the mold by increasing the number of U and V direction partitions. The experiment showed that the deformation during forklift transportation decreased by 36.5%, during lifting transportation by 13.9%, during paving deformation by 36.9%, and during hot pressing, the deformation of the tank was reduced by 18.2%. After optimization, the maximum deformation of the mold under conditions such as forklift transportation, lifting, and paving is similar to or slightly reduced from the original model. Meanwhile, the thermal deformation and quality of the mold decreased by 28% and 12.8%, respectively. The research results have important reference value for the design of composite material forming molds, helping to improve the performance and efficiency of the molds and reduce costs. By optimizing the design of the support structure partition, effective control of mold deformation can be achieved, and the stiffness of the mold can be improved, thereby ensuring the stability and reliability of the mold under various working conditions.