Slender robots are designed to work in narrow spaces, such as the disaster, the industrial equipment and the minimally invasive surgery. However, when these robots navigate such confined areas, it’s challenging to figure out the space shape and the robot position inside it. As a result, we cannot know the spatial position of the end effector inside the space, and thus cannot achieve localization of the robot. In order to solve this problem, it is necessary to consider the shape reconstruction and localization of the slender robot in confined environment. This chapter introduces four common and innovative reconstruction methods for different structure types and application scenarios of slender robots, including the traditional D-H method for slender robot with multiple linked segments, the near-end sensing and geometry estimation method for robots without end sensor feedback, the distal-end sensing method and the fiber brag grating sensing method for estimating the geometry shape. The body shape reconstruction is crucial for the control and application of slender robots, this chapter covers both fundamental and advanced techniques in this area.