The tie rod is the main load-bearing component of the clamping part of an injection building machine, typically possessing high strength and rigidity to withstand various forces such as mold expansion during the injection molding process. However, in the production of plastic products, especially during the high-speed production of thin-walled fast food containers, cutlery, and other items, fracture is prone to occur, resulting in significant economic losses for both customers and injection molding machine manufacturers. This paper establishes a finite element analysis model for the entire tie rod and nut assembly, analyzes and optimizes the stress concentration issues near the stress groove of the tie rod and the threads of the nut, obtains the dimensional parameters of the tie rod, and accumulates experience in the optimal design of the tie rod stress groove.