[Objective] A retrospective study was performed to evaluate the outcome of three-dimensional correction for adolescent idiopathic scoliosis(AIS)and discuss biomechanics of posterior three-dimensional correction surgery and measures for the prevention of spinal imbalance.[Methods]Thirty-one patients with AIS were classified and treated with three-dimensional correction surgery from 2005 to 2007.There were 18 male and 13 female with the average age of 15.2 years(range,11 to 18 years).The cases were classified according to the Lenke surgical classification,including type I 8 cases,type Ⅱ 4 cases,type Ⅲ 8 cases,type Ⅳ 2 case,type Ⅴ 5 cases,type Ⅵ 4 cases.The major curve Cobb's angles,the distance of apical vertebra shift and trunk shift,were measured and analyzed in the reoperative,postoperative and final follow-up radiographies.The average preoperative coronal Cobb's angle was 54?,the distance of both apical vertebra shift and trunk shift was 5.8 cm and 2.6 cm respectively.[Results]The mean time of follow-up was 16 months(range 1 to 3 years).The average postoperative coronal Cobb's angle was 21?,as the correction was 61%,the lost angle at the last follow-up was 4.0?.The postoperative distance of apical vertebra shift was 2.5cm,as the correction was 56%,the lost distance at the last follow-up was 0.5 cm.The distance of trunk shift at the last follow-up was 1.0 cm.[Conclusion]Posterior three-dimensional correction surgery is a good corrective method in the treatment of AIS.The spinal mechanical balance should be noticed during the operaion.