The welding process, a conventional production method of gate valves, has advantages such as light weight, but it also has disadvantages such high production price. However, the forging process, has economic merits and mass production capability. The main focus of this paper is the optimization of the preform in the forging process. This paper proposes an optimal design of the preform to improve the mechanical efficiency of the gate valve made by the forging method. The design of the preform is optimized by the use of the real response model to the Kriging model by computer simulation. Also, the optimized results were used to verify the response model. The verified response model confirmed the usefulness and reliability of the Kriging method in optimum structural design of preform achieved by finite element analysis and Kriging equations.