The process design of the thin-walled injection molding is investigated in this study. It was realized that the behavior of warpage in injection molding parts was affected by different process conditions such as melt temperature, mold temperature, packing pressure and injection rate. Experimental design of Taguchi method was used to determine the process conditions. Both the numerical simulations and experiments were conducted to study the effects of the process conditions on the warpage of a cap model. The proper processing parameters were also identified by the experimental design. The packing pressure was found to be the most important factor on the warpage of a thin-walled part. The experimental design done by numerical simulations also provided proper results in terms of warpage reduction.