Abstract: In order to improve the mechanical properties of nuclear-grade cast iron alloys, within the framework of the Six Sigma DMAIC quality improvement process, the chemical composition ratio was identified as a key factor affecting the mechanical properties of cast iron alloys. Through the use of Minitab analysis software and the design of experiment methods,a scientific chemical composition control scheme was determined. The results show that the composition control scheme developed through model selection effectively improves the mechanical properties of the cast iron alloy material, resulting in the production of a cast iron alloy product that meets user requirements and achieves the expected improvement goals.