In this paper, longitudinal control for a platoon as one dynamic model is investigated by simulation. Difficulty of treating a platoon as one dynamic model is due to non-linearity and uncertainty included in the characteristic of tractive and brake force. A robust model-matching controller is developed for solving the above problem. The characteristic of the tractive and brake force is equivalent to those of a specific transfer function by the model-matching controller. A longitudinal controller for platooning is developed with assumption that the model-matching controller works on each constituent of the platoon. Velocity of the leading vehicle and each spaces between the constituents can be controlled independently and smoothly by the longitudinal controller. The proposed control system is suitable for changing space as well as fixing space, and enables the platoon to execute intelligent tasks according to the various kinds of situations.