In plastic injection molding, the pressure of the melted plastic inside the mold cavity is very high. In addition to opening and closing of the mold, the plastic injection molding machines clamping system must resist the high pressure of the melt polymer plastic inside the mold cavity. When the plastic mold is at the mold locking stage, the injection molding machine’s mold clamping mechanism will apply extreme force on the entire mold. If the design of the core plate thickness, and number and position of support pillars are not based on scientific theories and too little steel is used in the mold, the mold service life will be reduced and it will affect the quality of the finished products and dimensional accuracy; if too much steel is used, it will result in the waste of mold materials and is also likely to enhance the demand on machine. Therefore, this study explored the structural characteristics of the entire mold in the plastic injection molding process, conducted experiments by changing the core plate thickness, number and position of support pillars, and measured the strain value of the core plate deformation during the injection molding process using a strain gauge. In addition, by combining CAE (Computer Aid Engineering) software, this study verified the experimental and simulated trends’ accuracy before adding the Taguchi method for the analysis of the simulated experimental design planning. We used CAE to analyze the deformation of core plate under different parameters and studied the core plate thickness optimization and support pillar effectiveness without damaging the plastic mold to further enhance the overall mold design.