Objective To report the reference values of spine and pelvis parameters in the normal population by analyzing the sagittal parameters in different age groups, and to explore the impact factors of maximal thoracic kyphosis (max TK) in different age groups. Methods A total of 191 asymptomatic healthy volunteers who took standing full spine anteroposterior and lateral X-rays at Center of Physical Examination, Affiliated Hospital of Shaoxing University of Arts and Sciences (101 volunteers) and The First Affiliated Hospital of Naval Medical University (Second Military Medical University) (90 volunteers) from Jan. 2015 to Jan. 2018 were enrolled. Demographic statistical data and sagittal imaging parameters of spine and pelvis were collected. The volunteers were divided into age≤40 years old group and age＞40 years old group, the sagittal parameters of different age groups were compared and analyzed, and the influencing factors of max TK in different age groups were analyzed. Results There were 94 volunteers in the age≤40 years old group with an average age of (28.5±6.4) years old, and 97 volunteers in the age＞40 years old group with an average age of (53.9±8.3) years old. In the 2 different age groups, there were significant differences in T₁ vertebral tilt (T₁ tilt; 18.6°±6.5° vs 20.6°±5.5°, P＝0.023), thoracic lower end vertebral angle (TVA; 15.3°±5.3° vs 17.5°±6.6°, P＝0.013), max TK (33.9°±8.3° vs 38.0°±9.4°, P＜0.001), maximal lumbar lordosis (max LL)-max TK (16.0° ［－9.0°-33.0°］ vs 12.0° ［－6.0°-41.0°］, P＝0.010), and sagittal vertical axis (SVA; －7.5 ［－58.0-48.0］ mm vs 9.0 ［－53.0-49.0］ mm, P＝0.005). T₁ tilt, TVA, max LL and sacral slope were positively correlated with max TK in the age≤40 years old group (all P＜0.01); age, T₁ tilt, TVA and max LL were positively correlated with max TK in the age＞40 years old group (all P＜0.01), while pelvic incidence was negatively correlated with max TK (P＜0.05). Conclusion Max TK shows a uniform increasing trend with age; especially in the population over 40 years old, max TK is positively correlated with age. The pelvic compensation for max TK changes shows different patterns at different age stages.