To improve the surgical precision of genioplasty, the authors develop and validate the precise repositioning instrument for genioplasty, which can guide the precise repositioning of chin bone segment truncated during genioplasty. The patent application for the precise repositioning instrument for genioplasty is already submitted (Patent No. 201410032051. 2, China). The accuracy of genioplasty can be improved significantly by using the precise repositioning instrument to locate the chin bone segment truncated. And this method is quick, simple, and safe.