Background The International Scientific Society on Scoliosis Orthopedic and Rehabilitation Treatment (SOSORT) proposes that the effect of brace treatment combined with physiotherapeutic scoliosis-specific exercises is significantly better than that of either alone. Wearing full-time rigid braces 23 h a day can effectively control the progression of scoliosis. However, long-term wearing of braces can cause psychological disorders, dyskinesia, lung function disorders, and other issues. Nevertheless, exercise can increase muscle function, correct the physical line, and compensate for the side effects of orthotic treatment. Objective To explore the clinical effects of wearing a full-time rigid brace for 20–24 h/day compared to a part-time rigid brace for 14–18 h/day combined with Schroth three-dimensional exercises on scoliosis correction and quality of life in patients with adolescent idiopathic scoliosis (AIS). Methods Sixty AIS patients were randomly assigned to the full-time brace group and the part-time brace combined with Schroth exercise group, with 30 patients in each group. Patients in the full-time brace group were treated with a rigid thoracolumbar orthosis and were required to wear it for 20–23 h/d. Patients in the part-time brace combined with Schroth exercise group were treated with Schroth three-dimensional exercise, with home and outpatient training together at least 5 times per week. The weekly training time was at least 4–5 hours, and the orthotic device was worn for 14–18 h/d. The two groups of patients were evaluated for Cobb angles and the angle of trunk rotation (ATR), thoracic expansion, and scoliosis research society 22-item (SRS-22) patient questionnaire before enrollment and after 6 months of treatment. Results In the intragroup comparison, Cobb angles, ATR, and thoracic expansion were significantly improved in the combined treatment group after 6 months of treatment compared to before treatment (p < 0.01), and the four indices of SRS-22 were improved before and after treatment, but there was no significant difference (p > 0.05). In the full-time brace group, there was a significant reduction in the Cobb angles (P < 0.01), but there was no statistically significant difference in the ATR, thoracic expansion, or SRS-22 before and after treatment. Comparing between groups, the combined treatment group showed greater improvement in Cobb angles, ATR, thoracic expansion, and the items of pain and psychology in the SRS-22 compared to the full-time brace group (p < 0.05). There were no differences between the two groups in self-image and function on the SRS-22 (P > 0.05). The satisfaction survey in the SRS-22 of the combined treatment group was better than that of the brace group, but there was no significant difference (P > 0.05). Conclusion The full-time brace and the Schroth 3D motion combined with a part-time brace both decreased the Cobb angle in AIS patients after 6 months of treatment. In addition, the brace combined with Schroth exercise showed significant improvement in the ATR, thoracic expansion, and psychological status and relieved pain. Adequate Schroth exercise can appropriately reduce the time of brace wear without affecting clinical outcomes and support brace treatment. Therefore, conservative treatment of idiopathic scoliosis with bracing combined with Schroth 3D exercise is recommended.