Abstract: Fuzzy PID has advantages that do not need to make accurate mathematical model and has a strong capacity of resisting disturbance. Auto adaptive cruise control system has been researched and has been built into a model of simulation, which are based of Fuzzy PID algorithm within the tool of simulink in this study. The system which is based on simple longitudinal dynamics of vehicle takes advantage of the relation between driving force and velocity to solve the problem that following when the vehicle is driving. The advantage of the system has simple model that controls the velocity of following vehicle through only controlling driving force and the model is without relating braving and throttle of vehicle. The results of simulating demonstrates that following system which its inputs of controller are the error of distance and the relative velocity between leading car and following car has a quite good character of following, fast response and safety performance.