Focusing on the forging process of an aeroengine GH4169 alloy disc component and addressing the challengesassociated with controlling grain size and uniformity, a simulation study was conducted on grain size evolution throughoutthe entire forging process. First, a strain-compensated Arrhenius constitutive model for describing the macroscopic flowstress and a dynamic recrystallization and grain growth model considering the influence of the δ phase were established.Second, considering the inheritance relationship of geometric and grain size data throughout the multistage forging process,a macromicro coupled finite element model was developed to comprehensively predict deformation and grain sizeevolution. Finally, the simulations reveal the grain size distribution and evolution throughout the entire process(upsetting-heating-preforging-heating-final forging). Upsetting and preforging achieve initial refinement of the originalmicrostructure through localized, nonuniform large deformation but result in an uneven grain size distribution. Intermediateheating processes, utilizing the difference in growth rates between large and small grains, promote grain sizehomogenization. During the final forging stage, under low-speed, near-isothermal conditions, sufficient dynamicrecrystallization is induced in the vast majority of the component, ultimately achieving significant overall grain refinementto an average grain size of ASTM 9.0~9.5. Only localized small deformation zones in contact with the die retain coarsergrains of approximately ASTM 7.5.