The shear-warp algorithm is used to reconstruct optical coherence tomography images (OCT) of the tooth in vitro. 3D reconstruction image is convenient for doctors to locate lesions and has a great potential for the clinical diagnosis of early dental caries. The basic principle of the shear-warp algorithm is introduced, as well as the all-fiber optical coherence tomography dental diagnosis system and three dimensional reconstruction image of the tooth in vitro based on 97 OCT images.