There has been an increasing trend of using the double-lift door glass regulating system for high end cars to expect a better regulating function. Parameter design was conducted to optimize the regulating system and improve the robustness of the system in the market. Besides using the traditional dynamic S/N ratio approach, standard S/N ratio was used for two-step optimization for comparison of the two approaches. It was confirmed as shown in this example that there was little difference on the results between the two cases when the linear term is significant.