Background: Spine health is significant in adolescent health. Few studies have focused on adolescent sagittal plane health; therefore, this study investigated the sagittal spine morphology and function of adolescents.Methods: This cross-sectional study analysed 1152 junior and senior high school students (543 boys and 609 girls) in Beijing. Spinal sagittal morphology and function of adolescents were measured using the Spinal Mouse. The sacral angle (SA), thoracic kyphosis angle (TKA), lumbar lordosis angle (LLA), inclination angle (INA), sacral range of motion (SROM), thoracic range of motion (TROM), lumbar range of motion (LROM), and inclination range of motion (IROM) were measured. The Matthiass strength test was used to measure changes in angles after external load placement on the adolescent spine.Results: Abnormal TKA rates were 48.2% and 44.7% in the junior and senior high school groups, respectively. Abnormal LLA rates were 44.6% and 55.4%, respectively. Spinal mobility test results of the junior high school group were 60.6°±19.1° (SROM), 23.0°±16.6° (TROM), 81.3°±15.4° (LROM), and 136.1°±16.9° (IROM) for boys and 66.0°±34.4° (SROM), 14.0°±17.3° (TROM), 66.3°±18.6° (LROM), and 127.4°±26.8° (IROM) for girls. For the high school group, these results were 66.0°±17.6° (SROM), 21.6°±16.0° (TROM), 77.9°±15.1° (LROM), and 138.4°±16.0° (IROM) for boys and 72.2°±26.9° (SROM), 15.7°±17.2° (TROM), 65.8°±18.2° (LROM), and 133.4°±21.7° (IROM) for girls. There were significant differences between boys and girls (P<0.05 or P<0.01). The Matthiass strength test results indicated that the inclination angle change (INAc) values of the junior high school group were 5.7°±5.0° and 2.6°±3.7° for boys and girls, respectively; however, the INAc values of the senior high school group were 2.8°±3.3 and 1.6°±3.0 for boys and girls, respectively, indicating significant differences (P<0.01). The canonical correlation coefficients of SA, SROM, LROM, and IROM were 1.3877, -2.5384, -0.6625, and 1.6336, respectively. SROM and LROM were negatively correlated and IROM was positively correlated with spinal function.Conclusion: Thoracic kyphosis and lumber lordosis rates were high. During flexion and extension, Boys had better thoracic and lumbar vertebral activity and overall activity. Girls had better ability to maintain the normal spinal shape with an extra load. Sacral obliquity and pelvic position greatly influence the spinal morphology.