This article explores the distribution and evolution of the internal grain structure of large-sized GH4738 alloy during the complex continuous deformation blanking process, based on the process sequentiality and organizational heredity, by employing a finite element model combined with secondary development methods. It presents a general approach for process design and outcome prediction. This paper conducts finite element simulation calculations based on the actual billet preparation process of φ660mm grade GH4738 superalloy, comparing the simulation results with the grain size at corresponding positions of the actual billets to verify the reliability and accuracy of the established model. Utilizing this model, typical upsetting and cogging processes are analyzed, and the effects of process parameters on the microstructural evolution of the billet during multiple deformation passes are discussed, along with methods for process formulation. During the upsetting process, as the reduction speed increases, the deformation temperature decreases, and the reduction amount decreases, the degree of dynamic recrystallization within the billet diminishes. In the cogging process, as the reduction speed decreases, the cogging temperature increases, and the feed amount decreases, the degree of dynamic recrystallization within the billet increases. Furthermore, based on the specific analysis in this paper, it is recommended to control the reduction speed during the upsetting process between 5mm/s and 12mm/s; the initial upsetting temperature should be 1160°C; and the single-pass reduction amount should be controlled between 25% and 35%. The cogging process is more complex than the upsetting process. Taking into account factors such as grain refinement within the billet, surface temperature drop during the cogging process, and the occurrence of the "concave center" phenomenon, it is recommended to control the reduction speed between 60mm/s and 90mm/s; the second cogging temperature should be chosen between 1120°C and 1130°C; and the feed amount should be controlled between 200mm and 350mm.