This paper presents the results of orthogonal simulation experiments conducted on the deformation temperature, friction factor, and deformation rate of process parameters for large modulus spur gears made of nickel based alloy GH738 with coarse grain size and non-uniform distribution, as well as other forming defects observed during hot forging and forming. These experiments were performed using DEFORM 3-D simulation software to optimize the combination of process parameters. During the experimental process, the evolution of the micro-structure and the impact of each factor on the average grain size and dynamic recrystallization volume fraction were observed. The influence level of each factor was then analyzed, and the optimal combination of process parameters was derived a deformation temperature of 1050°C, a friction factor of 0.35, and a deformation rate of 55 mm/s. For the initial grain size of a 42 μm billet, after forming the gear tooth grain size uniformity, the dynamic recrystallization volume fraction reached 0.988, with an average grain size of 14.1 μm and a local grain size grade of 9. The forging and forming effect is optimal, with a relatively complete dynamic recrystallization reaction. The process parameter settings for the high temperature nickel based alloy gear precision molding provide a theoretical basis for improving the efficiency and quality of gear production.