In order to realize the servo control of electro-pneumatic clutch actuator in an automated mechanical transmission, an electro-pneumatic clutch actuator system was established. By performing a simple sliding mode control law of dead zone directly on the established system, the tracking control of the electro-pneumatic clutch actuator without unnecessary control chattering was achieved. Meanwhile, the load characteristics of clutch could be estimated indirectly by the pneumatic driving force during trajectory tracking. In theory, the estimation error of load characteristics obtained by this approach is small. So, the clutch load characteristic is closer to the actual value in the trajectory-tracking control. Tests show that the proposed model-based integral sliding-mode controller with the estimation of clutch load characteristic introduced can improve the tracking accuracy to a large extent.