With the development of new energy vehicles, the number of electronic control units (ECU) and their brackets are increasing. The use of plasticization for ECU bracket can significantly reduce weight and cost, but it is necessary to solve the flatness issue caused by warpage deformation. Based on computer aided technology, the process optimization scheme of injection molding flatness of ECU bracket was explored. Aiming at the issue of excessive flatness in the initial process, an orthogonal test was designed and analyzed with mold cavity temperature, injection time, holding time, and melt temperature as independent variables. The results show that the influence of mold cavity temperature on flatness is extremely significant. The influence of injection time and holding time on flatness is significant, while the influence of melt temperature on flatness is not significant. The optimized process parameter combination is A₂B₁C₃D₂. The simulation results of the optimized process show that the flatness is decreased from 8.685 2 mm in the initial process to 3.978 2 mm, with an optimization rate of 54.2%, which meets the design requirements and has a good appearance. The appearance status and flatness test results of the trial mold samples based on the optimized process meet the requirements, thus verifying the correctness of the optimized process in the article.