Objective To evaluate the curative effect of selective screw placement of posterior three-dimensional correction for LenkeⅠadolescent idiopathic scoliosis (AIS), and to compare the effects of different screw densities on the orthopedic parameters. Methods We retrospectively analyzed the clinical data of LenkeⅠAIS patients undergoing posterior correction of scoliosis+selective fusion and internal fixation surgery in Department of Spine Surgery of Changhai Hospital of Naval Medical University (Second Military Medical University) between Jan. 2013 and Jan. 2017. According to the references, the screw density was defined as the number of nails/(fusion segment×2). The patients were divided into high density group (screw density>0.7) and low density group (screw density ≤ 0.7). The general characteristics, surgical correction rates 2 weeks and 2 years after operation, loss of correction rate after 2 years and correction ratio were compared between the two groups. Results A total of 36 eligible patients (11 males and 25 females) with LenkeⅠAIS were included in this study, with an average age of (13.97±1.89) years old. There were 23 cases in the high density group and 13 cases in the low density group, with the screw densities being 0.80±0.04 and 0.64±0.06, respectively, and the difference was significant (t=10.799,P<0.01). There were no significant differences in gender, age, brand of pedicle screw, preoperation coronal main curve Cobb angle, preoperation bending Cobb angle or preoperation scoliosis flexibility between the two groups (all P>0.05). Compared with the high density group, the low density group had no significant disadvantages in coronal main curve Cobb angles 2 weeks and 2 years after operation, surgical correction rate 2 weeks after operation, or loss of correction rate 2 years after operation (all P>0.05). Pearson correlation analysis showed that there were no significant correlations between screw density and surgical correction rate 2 weeks after operation, correction ratio and the loss of correction rate (r=0.149, 0.348, 0.217; P=0.387, 0.874, 0.177). Conclusion For LenkeⅠAIS patients with better flexibility, appropriate reduction of the nail number in selective screw placement surgery may not adversely affect the short-term and mid-term outcomes.