An adaptable stiffness of mechanical using wire rope tension control, called as a twin direct-drive motor system, has unique advantages in human-robot interaction system, when compared with conventional industrial robot. Since the wire rope is low friction and lightweight device, it is possible to achieve high-efficiency, high degree of reliability, and safety. In this paper, modeling and closed-loop identification of the twin direct-drive motor system with wire rope tension are considered. After the swept-frequency sine wave injection and output data collection are finished, the Box-jenkins model is employed to identify the frequency response. From the simulation and experimental results, the total stiffness of the twin direct-drive motor system and the bandwidth of mechanical system can be increased by changing wire rope tension. This feature may make the twin direct-drive motor system very useful to provide a safety and smooth interaction force during operation. Therefore, it is suitable to implement with the human-robot applications for example, arm movement training robot and motion guide robot system.