A method for reconstructing joined part surfaces of two adjacent teeth of a 3D digital model of teeth is provided. The method includes: obtaining a 3D digital model of teeth which includes adjacent first tooth and second tooth having joined surfaces； identifying a set of intersection points of the joined surfaces； fitting a first plane using the set of intersection points； identifying a set of first control points from points on the 3D digital model of teeth near the set of intersection points basis curvature, where the set of first control points defines boundary of a first part surface of the first tooth to be reconstructed； reconstructing the first part surface using a linear equation system constructed basis the first plane and the set of first control points.
