The first part of the present paper presents a simple algorithm of the ABS operation in a quarter vehicle model. In the second part, the optimum and effective domain of friction of coefficient is obtained by the simulated program. It is concluded that decreasing friction of coefficient domain or increasing the friction of coefficient magnitude will reduce the stopping distance and stopping time. The modeling of brake has been done in the simulink of Matlab software. The desigend model is completely parametric and can investigate the effect of different variables in different conditions.