The warping deformation is an important index to evaluate the quality conformance of snap-in plastic plate assembly. Applies the Taguchi’s Design of Orthogonal Experiment (DOE) with the combination of mold flow project analysis module to study the warping deformation of the products. Through robust optimal design of injection molding process parameters and the experimental analysis, obtains the optimal process parameter combination, and by utilizing the calculations in the confidence intervals, verifies the reliability of the optimal parameter combination. The research results show that the dwell time is the most significant influencing factor, followed by cooling time, the plastic temperature and dwell pressure. The long dwell time and cooling time is easy to cause the increase of internal stress in products, which may leads to the possibility of warping deformation.