Abstract: To address the casting challenges of ZG275 cast steel valve body castings, such as its complex structure, uneven wall thickness, and susceptibility to shrinkage porosity and cavities, a sand casting process design and numerical simulation optimization was conducted in this paper. Based on the structural and material characteristics of ZG275 castings, a horizontal pouring scheme with a semi-closed intermediate gating system was designed. Alkaline phenolic resin sand was selected for molding, and parting surface, machining allowances, sand cores, risers, and chills were designed accordingly. Simulation software was employed to analyze filling and solidification processes of the initial sand casting process, and the locations and distribution patterns of defects were obtained. Process improvements were made by adjusting the number and placement of risers, adding insulating sleeves, and optimizing chill parameters. The optimized simulation results indicated that the shrinkage porosity and cavities in the optimized valve body casting were effectively controlled, achieving a casting yield of 67.7%, which can serve as a reference for the process design of similar valve body steel castings.