The invention relates to a method for converting pixel data of a tooth CT image into 3D printing data, and belongs to the technical field of image processing. The method comprises the steps of acquiring a CT image of a tooth, extracting pixel data of the image so as to generate pixel contour point cloud, acquiring outer surface point cloud of the tooth, performing coarse registration and fine registration on the pixel contour point cloud and the outer surface point cloud, respectively forming fine registration point cloud databases, setting a judgment value, verifying a fine registration result, combining the fine registration point cloud databases, acquiring a complete point cloud database of the tooth, rebuilding a three-dimensional grid database based on the complete point cloud database of the tooth, and forming an STL format supported by 3D printing equipment. According to the invention, a slice contour high-precision extraction method is adopted to realize adaptive extraction in order to adapt to a non-free curved surface of the tooth surface, CT scanning and non-contact scanning are combined innovatively, and existing mature algorithms are integrated, thereby realizing conversion of the pixel data of the tooth CT image into the 3D printing data, effectively improving the image conversion efficiency and precision, and being high in pertinence.