Abstract: The invisible orthodontic surgery depends on pre-alignment of the misplaced teeth.Based on this requirement,a computer aided invisible orthodontic treatment system consisting of tooth shape modeling and virtual treatment planning is proposed.The input of the system is a digital dental model obtained by optical scanning and the output is the intermediate models ready for rapid prototyping manufacturing.The system consists of the following main steps: tooth segmentation,tooth restoration,tooth movement design,gum deformation,orthopedic scheme determination and virtual occlusion.The tooth model is segmented from the dental model using a two-step procedure.The segmenting region is firstly searched by exploiting the geometry features,and then the boundary is trimmed out by projecting the control curves.By specifying positional constraints using a network of control curves,the missing region between adjacent teeth is repaired based on differential coordinates.For gum deformation,the moving least-square interpolation scheme is employed to solve the problem on excessive consumption of memory space when solving the large-scale linear system.This system is the key step to manufacture invisible aligners.It also provides a visual environment for diagnosing the illness.Clinical trials on 50 cases show that our invisible orthodontic treatment system provides an efficient orthodontic treatment method.