The molding process can be divided into five separate steps: plastification, injection, holding, cooling, and finally ejection. In the plastic injection molding, the effect factor such as mold temperature, injection speed, packing pressure and inhomogeneous cooling under packing process affects both the article dimension and physical characteristics. Especially, the packing pressure is the most critical factor to affect molded articles quality among the packing parameters. In this paper, the CAE simulation considering the molding condition is performed to predict the faulty cause which appears in the packing process between cavities of injection molding machine. From the results of CAE simulation, the packing phenomena according to the product form and the gate position was investigated to improve the article quality and minimize the various molding defects. The effect of packing pressure and gate number on the injection molding was discussed.