This paper mainly focuses on the mandible surgery application of the rapid prototyping technology and the medical CT technology. The relation of the common approach of CT image data processing was discussed in this paper, and an improved construction method of the rapid prototyping data of jaw bones based on CT image was proposed as well. A 3D model of the mandible defect was generated after the CT data processing. An individual tray was designed by using mimics software and fabricated by rapid prototyping (RP) technology. The method proposed in this paper could improve both the reconstruction rate and the geometric similarity.