In recent years, a lot of studies on brake of car aims to reduce stress, vibration and noise of the brake on vehicle. In this paper presents a sensitivity analysis of pressure and friction coefficient effect to stress of disc brake. Base on this result, an optimization for brake by stress constraints was performed. The results are shown that the contact area between disc brake and pad also it’s stress and pressure. Studies also have shown relationships between pressure, friction coefficient and stress of brake. After that, we optimize the model of disc brake by stress constraints to obtain the new model better. This is a pre study for studies on dynamic and vibration of disc brake.