A side collision of an automobile poses a higher risk of injury compared to those of a frontal collision. Therefore governments and insurance companies establish and implement new safety standards in order to ensure the safety of the occupants throughout the world. Most of the suggested standards aim to reduce the Head Injury Criterion (HIC). Widely used side airbag systems, including the curtain airbag, are known to be the most effective means to reduce HIC, but designing a curtain airbag is a very difficult task due to the non-linear characteristics of HIC and the airbag deployment mechanism. These difficulties cause an airbag engineer to choose design variables more cautiously and seek more effective design methods. This paper introduces the curtain airbag design procedure which uses current optimization methods in order to reduce the HIC risks of the occupants. First of all, it defines various elements of the curtain airbag as design variables, performs a computer-based analysis based on the Analysis of Variance (ANOVA) technique, and then selects and defines design variables important to the head injury criterion. These defined variables and the Orthogonal Array (OA) test to reduce the head injury criterion were used. The Response Surface Method (RSM) was used as an approximation method. The results were reviewed and compared in order to find a design solution to minimize the head injury criterion. These test results will give effective design methods for curtain airbag engineers.