(1) Background: This meta-analysis aims to systematically assess the effect size of Schroth three-dimensional exercise training on adolescent idiopathic scoliosis, especially for Cobb angles, angles of trunk rotation, and quality of life. (2) Methods: Randomized controlled trials (RCTs) focused on the effect of Schroth exercise on patients with adolescent idiopathic scoliosis (AIS) were retrieved from six databases, including PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang. All publications until July 2023 were searched. Two researchers screened and evaluated the literature. Review manager (RevMan 5.3) statistical software was used for meta-analyses, and subgroup analysis and sensitivity analysis of the literature with high heterogeneity were further conducted. (3) Results: In total, 14 studies were included, including 538 adolescent idiopathic scoliosis patients. Compared with conventional physical therapy, Schroth 3D exercise training is more effective at reducing the Cobb angle (WMD = −3.32, 95%CI [−4.15, −2.50], p < 0.001) and improving the trunk rotation angle (WMD = −2.24, 95%CI [−3.00, −1.48], p < 0.001), quality of life (SMD = 2.80, 95%CI [1.53, 4.06], p < 0.001), and WRVAS (WMD = −2.92, 95%CI [−3.25, −2.60], p < 0.001), as well as enhancing the strength of the lumbar extensor (SMD = 1.79, 95%CI [1.46, 2.12], p < 0.001). (4) Conclusion: Compared with traditional therapy, Schroth 3D exercises are more effective at decreasing the Cobb angle and ATR in adolescent idiopathic scoliosis, improving patients’ quality of life, as well as enhancing the strength of the lumbar extensor.