A three-dimensional (3D) shape measurement method for confined space using an optical tube is proposed. Considering small cross-sectional area and high reflectivity, a optical tube is designed for image transmission. With the optical tube, fringe patterns can be easily projected onto internal surface from external space. The collected images transferred from interior space to external space are recorded by CCD. Accordingly, shade and occlusion caused by the limitation of measurement space are avoided and 3D shape measurement for internal surface of confined space is realized. Experimental results show feasibility and validity.