Continuum robot is a class of robots renowned for its significant flexibility and manipulability. In recent years, tendon-driven robot, one type of continuum robots, is with compressible and extensible length and bigger working space compared with the non-extensible robot and can travel along the nonlinear spatial curved path. However, existing retractable robots mainly consist of a concentric-like tube, by which it is hard to construct a robot with arbitrary segments, due to the iterative reduction of diameters of multiple tubes and the constraint that diameters of tubes should not be over small to guarantee a necessary stiffness. In this paper, we present a novel tendon-driven continuum robot with extensible length to overcome this shortcoming. The key distinction is that the new design achieves extension based on wire-driven method rather than direct push-pull approach adopted in existing concentric robots. Therefore, continuum robot based on this new design shows higher flexibility and can be with arbitrary segments. Kinematic model of the robot are derived and its workspace is obtained for one and two bending modules. Prototype built demonstrates via experiments the contractible and extensible performance, and the maximal bending angle is measured through experiments. This type of continuum robot may be implemented in therapies for some clinical diseases, like neurosurgery and natural orifice transluminal endoscopic surgery (NOTES). © 2018 IEEE.