Robotic technology is used widely today because of their advantages to support human operator. Robot systems have been used, not only for industrial processes, but also for a wide range of applications, such as minimally invasive surgery. To perform complicated surgical operation with robot system, the flexible actuator which is composed of a linear motor and a thrust wire, has been proposed. From the previous research, the force transmissibility of the trust wire is evaluated. It seems that the performance of the flexible actuator depends on a shape changes of thrust wire. This is because, a thrust wire has friction effect. This paper deals with a new mechanical design of trust wire with the miniature stroke. The miniature stroke which is consists of a shaft, ball cage and nut, is applied in the flexible actuator to achieve high accuracy, minimal rolling loss and rolling motion with extremely low friction resistance. By using the proposed method, the improvement of position response and force sensation can be obtained. The effectiveness of the proposed method is verified by the friction force identification.