Dental decay and erosion have been very common these days.Current diagnosis often depends on the experience of the dentists and is lack of quantification.In this paper,a new scanning system which collected structural information of tooth surface and enamel-dentine junction is introduced.A 3D translation device was used to control the moving trajectories of an A-mode transducer so as to acquire the echoes from the whole surface of a tooth sample.Based on this system,the tooth enamel in a 3D form could be reconstructed.Due to the gain compensation method that applied to radio frequency signals,no special preparation was required before scanning and the 3D reconstruction of the whole tooth could avoid poor positioning encountered in early works.Despite some discontinuous areas appearing in the 3D image,the 3D representations of human molars well duplicated the real samples and the thickness of enamel could be measured.