To develop the pressure control algorithm for active braking of adaptive cruise control (ACC) system,a test bench with real parts of the tested vehicle is built.With the dynamic analysis of the active braking actuators,it is demonstrated that different duty of pulse-width modulation (PWM) signals could control the pressure changing rate of the wheel cylinder.To obtain that signal,a modified proportional-integral -differential (PID) control algorithm is developed using the variable parameter method,the control value reset method,the dead zone method and the integral saturation method.Experimental results show that the delay and overshoot of the pressure response could be reduced considerably using the modified PID algorithm compared with the conventional one.The proposed pressure control algorithm could be used for the further development of the ACC’ s controller.