There are lots of plastic components produced by using injection molding process. The plastic parts are used in the most of practical applications such as electronics, automotive, medical, aerospace, and construction areas. The plastic product is normally lowed its quality by some defects appeared on the molded part such as warpage and shrinkage. The injection molding process is controlled via adjusting the injecting process parameters to get the high quality of final parts such as minimizing the warpage of product. This paper demonstrates the design of experiment method (DOF) with Taguchi technique to investigate the effect of process parameters on warpage of injection molded parts during injection molding process. By Taguchi method, the orthogonal array is designed to optimize warpage via controlling the influencing factors of melt temperature, mold-open time, and cycle time. ANOVA analysis is used to figure out the most effect of the parameters on the warpage. The results show that the melt temperature has highest effect on the warpage, the second position is cycle time, and third factor of mold-open time has smallest effect on the warpage.