CFD three-dimensional numerical model of the cavity flow field of the mold was established, and the numerical simulation analysis was carried out on the different open hole ratios and different layout positions of the air distribution plate. The results show that the velocity distribution in outlet cross section of back cavity was very uneven without air distribution plate, while it was obviously improved after air distribution plate was added. With the opening rate increased from 5%, 10%, 15%, 20% to 25% sequentially, the airflow uniformity decreased accordingly. With the air distribution plate location from the entrance of mold back cavity L increased from 90, 100, 110, 120, 130, 140 mm in proper order, the airflow uniformity firstly increased but then decreased, and the airflow distribution is optimum when it was 120 mm. Based on the determination of the structure and position of the air distribution plate, the position of the back cavity is further optimized, and the local energy loss of the airflow could be reduced. The average velocity of the airflow in the outlet cross section is increased by nearly 11% with further improvement in the efficiency of product release.