In this study, the three-dimensional modelling of the gearbox was carried out by UG 12.0 software to ensure the accuracy and completeness of the geometry and dimensions of the model, which provided the basis for the subsequent injection moulding simulation analysis. After the model was constructed, injection moulding simulation analysis of polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer (ABS) and polycarbonate (PC) were carried out to verify the injection moulding processability through Moldflow software. In order to predict the warpage behaviour, the best combination of optimized process parameters was derived by inputting the parameters obtained from the fitting of the dual-domain Tait model and Cross-WLF model into Moldflow software for simulation calculations during the simulation verification stage. The simulation results showed that the warpage deformation of the fabricated parts was significantly reduced under the optimized process parameters. Under the optimized process parameters, the actual warpage deformation of PBT, ABS and PC parts was reduced by 90.32%, 89.81% and 90.89%, respectively.