Abstract: Based on the numerical simulation analysis,the influence of structure size on the dimensional accuracy of the precise injection molded plastics parts was studied in the same processing conditions.The study found that for plastics parts of inhomogeneous thickness,the aspect ratio of the cross section to the thickness played an important role,but the length played a moderate one.Through orthogonal experiments and optimization analysis,structure size injection molded met the design requirements of precise injection molded plastics parts.