Aiming at the lightweight design of the frame-type composite material forming mold, an optimization method based on response is proposed. This method takes the optimized size variables and optimization goals as input and output respectively, and establishes and fits corresponding approximate mathematical models through methods such as sensitivity analysis and test table design. After setting lightweight optimization goals and constraints, the problem is solved by the mathematical model and is used to obtain the optimal solution. Solution results are substituted into the finite element model for calculation and comparison to verify the accuracy of the solution. A specific mold is used as an example to illustrate the use of the method.