In the plastic design and development of PLC controllers, the key is to control the flatness and deviation of the installation hole axis. The article uses simulation technology to calculate the flatness and axis deviation of the PLC controller after injection molding, and designs orthogonal tests to explore the influence of process parameters and optimization schemes. The orthogonal test results indicate that the maximum values of the flatness and axis deviation of the PLC controller under different combinations of process parameters are 2.5 times and 1.8 times of the minimum values, respectively, indicating that the influence of process parameters is significant. Taking into account the flatness or axis deviation, the optimal process parameter is A₂B₂C₃D₁. The simulation results of the optimized process show that the shrinkage estimation and gas cavity on the main appearance surface meet the requirements, and the injection pressure and clamping force are also within the normal range, verifying the feasibility of the optimized process.