Objective To build up a new contour and functional reconstruction technique of mandibular defects with rapid prototyping and reverse engineering technique. Methods From April 2002 to August 2004, 4 cases of mandibular defects due to resection of large mandible lesion were treated. Of 4 patients, there were 3 females and 1 male, with an age range of 21-42 years, which underwent secondary operation and presented a deviation as mandibular movement. The openingmouth extent was 1.8-2.5 cm(2.2 cm on average). The data of defects area were renewed withMimics and Geomagic Studio software; and the titanium reconstructive frame was designed and manufactured with rapid prototyping technigue. Defect were reconstructed by using CT digital data of patients. Results The CT data could be used by image software directly. The implant design could be completed by computer-aimed design(CAD)/computer-aided manufacture(CAM). The resin model and titanium frame were manufactured accurately by RP technique. Four patients achieved one stage healing. After a follow-up of 3 months to 2 years, largemandibular defect was reconstructed satisfactorily and the opening-mouth extent was 3.03.4 cm(3.2 cm on average). The occluding relation was normal. The implant denture was put on and the mastication function was good in 1 case. Conclusion Individual design and repair of large mandibular defect with CAD/CAM techniques is worth extending application clinically. It is a simple and accurate method.