Objective To build a method of mandible 3D model to measure and analysis, then to finish the operation simulation, providing anatomic data to avoiding the complicafious of mandible osteotomy. Methods Using CT data to reconstruct 3D model of mandible with blood vessel and bone, then using Simpleware to measure and analysis, and using Freeform system and an incision method of Boolean to simulation mandible osteotomy safely. Re, tits It was possible to use CT data to rebuild 3D model for 3D measure and analysis for operation simulation. The inferior alveolar artery and never were the main tiasues which went through the madibhilar. The length of mandibular foramen to anterior minus was (19.13±0.66) ram,and the ones to posterior ramus was (18.96± 0.64)mm. The angle of the mandible was (109.70±4.67)°. The rages of the remus for safe operation was (12.62±0.28)mm, and the safe rages about angle of the body and bottom of the mandible was (22.30±4.67)°. There were obvious differences from children to the aged in the mandible physiological and anatomic study. We can use Freeform system to simulate the operation on 3D model. Conclusion It is a new method to build 3D model and use Freefonn system to simulate operation and a new path to communion with patients for a good operation.