Most cases of facial asymmetry involve yaw deformity, and determination of the yaw correction level is very difficult. We use three-dimensional soft tissue simulation to determine the yaw correction level. This three-dimensional simulation is based on the addition of cephalometric prediction to gradual yaw correction. Optimal yaw correction is determined visually, and an intermediate splint is fabricated with computer-aided design and computer-aided manufacturing. Application of positioning devices and the performance of horseshoe osteotomy are advisable. With this procedure, accurate repositioning of jaws was confirmed and patients obtained fairly good facial contour. This procedure is a promising method for a widespread, predictable treatment of facial asymmetry.