In this prospective study, the effectiveness and biomechanical factors of spinal orthoses in the treatment of moderate adolescent idiopathic scoliosis (AIS) patients were investigated. In the first 20 months of orthotic treatment, the values of standing AP Cobb's angle, apical vertebral rotation, lumbar lordosis as well as thoracic kyphosis showed significant reduction (P<0.05), however, the angle of trunk inclination and trunk listing did not. The values of those reducible parameters reached their lowest values within the first 12 months of orthotic treatment and then the values gradually increased but they were still below the pre-brace values. The mean pressure of The pressure pads was found to be 7.09 +/- 1.77 kPa (53.2 +/- 13.3 mmHg) while the mean tension of the straps was 26.8 +/- 5.2N. The standing AP Cobb's angle strongly correlated with the pad pressure (correlation coefficient=0.931, p<(.05) and strap tension (correlation coefficient=0.914, p<0.05). The strap tension and pad pressure strongly correlated and the correlation coefficient was 0.873 (p<0.05). This suggests that in the consideration of biomechanical function of spinal orthoses, the focus may be upon how tightly the orthosis was fastened and if the location and direction of the pressure pads are the correct. Therefore, for enhancing independent standard tension should be set in each strap, and regular and close monitoring is needed.