A plastic injection mold for injection of a 100min long and 70mm width plane connected to a 20 mm height vertical side wall by a radius of 5mm fillet is investigated in this study. Four different part thicknesses, 2mm, 1mm, 0.75mm, and 0.5mm, respectively, are designed to study the thickness effect upon the warpages of plastics. Three different plastics, ABS(PA-756; Chi-Mei), PC(HF111 OR; GE), and PP(PRO FAX 6331) are injection molded by the designed mold. Taguchi method is used to find out the optimum injection molding condition for each of the experimental measurement and the CAE analysis. Cavity pressure sensors are embedded in the mold to detect the inner pressures and temperatures of the melts. A 3D laser scanning system is used to measure the deformations of plastics after injection molding. Cavity pressures and deflections of the experimental measurement and the CAE analysis are compared to show the effects of molding parameters to deflections. The experimental measurement and the CAE simulation show some discrepancies in deformations which may attribute to the experimental errors or the theoretical assumptions in mold flow analysis and the used material models. In general, the deformations by experiment show greater values than the deformations by simulation.