Abstract: In this paper, a mold flow analysis was performed for an automobile builtin storage box by Moldflow software according to the rheological principle of polymers. Aimed to the defects of the storage box occurring during the injection molding process, which included the surface sink marks, long time to reach the ejectiopm temperature and the large warpage deformation, the gating and cooling systems of the mold were redesigned. These defects were found to be eliminated or reduced through an evaluation for the quality of the injectionmolded product. The shrinkage index was reduced from 0.638 2~4.009 to 0, the time to reach the ejection temperature was reduced from 37.92~92.68 s to 19.87~21.40 s, and the total warpage deformation decreased from 1.166~1.782 mm to 0.024 0~0.416 5 mm. These results indicated a significant effect. Based on the above results, the injection mold of the automobile builtin storage box was designed and the qualified parts were produced by using this mold.