In this work, an on-the-move (OTM) antenna which is mounted on ground vehicles and is used for communication between vehicle and satellite was studied. Since vehicles move during communication, active antenna line-of-sight (LOS) stabilization is a core technology to guarantee satellite communication quality. Stabilization control of the antenna LOS which is driven by a motor coupled with gears and flexible driving shafts was investigated. In consideration of the finite stiffness of the shaft and disturbance torque due to vehicle motion coupled with gear ratio, a stabilization control is proposed. The proposed control is based on an integral sliding mode method (SMC). Since this SMC is robust and chatter free, it gives fine stabilization performance and is easy to implement without consideration of wear and tear on actuators. The feasibility of the proposed control design was verified along with some simulation results.