The Automotive Interior Parts offer convenience and riding comfort for passengers. One of its main features is that it is placed in a conspicuous place. Therefore, automotive interior part manufacturer attach importance to appearance quality. Additionally, appearance quality of Interior Parts is more important as the senses of passenger heighten.Most Automotive Interior Parts manufactured by Injection Molding to mass produce it with complex geometry. But there are numerous defects in method of Injection Molding. Especially, large products like automotive interior parts are disadvantage. A typical example of defects is weld line, sink mark, short shot. These are having an adverse effect on the appearance quality as well as another quality like BSR (Buzz Squeak Rattle) and Side impact performance.In order to improve problem, molding has been modified and spray coating has been done over the past. But these solutions are giving rise to another quality problem like molding crack, deterioration of scratch resistance. And its solution is not environmentally-friendly. For these reasons, Injection Molding Process on Automotive interior parts is in want of a fundamental solution using optimization concept. But Optimization did not apply to Injection Molding actively in the meantime. Because it is composed of very complex factors and there is no quantification method on phenomenon of defects.This study suggests about new process to optimization of injection molding using quantification model and d-optimal method. As a result, the appearance quality index is improves by about 55% and injection pressure is reduced by about 28.4% in comparison with the initial model.