Abstract: objective: The aim of this study was to evaluate the accuracy and safety of ball tip technique in pedicle screw placement in adult degenerative scoliosis by comparing with the conventional freehand technique. Methods: From March 2014 to January 2019，A total of 30 cases with adult degenerative scoliosis treated with Posterior thoracolumbar scoliosis orthopedic surgery in our department were enrolled.They were divided into group A and group B. In group A, there were 5 males and 10 females with 178 pedicle screws, aged 63.1±7.1 years old. In group B, there were 6 males and 9 females,with 172 pedicle screws,aged 64.2±9.9 years old.Traditional freehand technique for pedicle?screw?implantation was applied in group A，while ball-tip technique was applied in group B. The accuracy and mean time of screw placement were compared between two groups.Result: The accuracy of screw placement was evaluated by postoperative CT scans according to the Gertzbein and Robbins classification. There were 145（81.46%）perfect screws,162（91.01%）clinically acceptable screws and 16（8.99%）fault screws in control group.There were 153（88.95 %）perfect screws,167（97.09%）clinically acceptable screws and 5（2.91%）fault screws in experimental group.Statistically?analysis?showed?the perfect and clinically acceptable screw placement ratio of experimental group was significantly higher than those of control group.The mean time of screw placement was respectively 2.87±1.15 min in control group and 3.12±2.20 min in experimental group.There was no statistically difference between two groups.There were no pedicle screw associated complications such as cerebrospinal fluid leakage, deep incision infection or spinal nerve and vascular injury in both groups.Conclusion: In orthopedic surgery for adult degenerative scoliosis, the ball-tip technique,without increased operation time,shows higher accuracy than the traditional freehand technique,being a reliable and safe method for screw placement.