Objective To compare the bone mineral density and age?related bone loss rate of thoracic and lumbar vertebrae using quantitative CT（QCT）， and to explore the feasibility of measuring bone density and bone loss rate using thoracic QCT. Methods A total of 708 patients who underwent full abdominal CT scans due to trauma， acute abdominal disease， and health examination from March 2022 to March 2023 were selected. The average BMD of T10 to L3 vertebral bodies were measured using quantitative CT software. The subjects were divided into several age groups according to the age of every 10 years. The average bone density and the age?related annual rate of bone density loss of the thoracic and lumbar vertebrae for each group were computed， the correlation analysis between thoracic and lumbar BMD and age was conducted using Pearson correlation analysis. Results The peak BMD for both males and females was in the 20 to 29 years age group. After the age of 30， the bone density of the thoracic and lumbar vertebrae began to decrease to varying degrees. For females aged 80 to 89， the cumulative bone loss rate for the thoracic and lumbar vertebrae was 60.61% and 61.34%， respectively， while for males， it was 44.45% and 49.35%， respectively. The BMD of the thoracic and lumbar vertebrae in both males and females showed a negative correlation with age （P < 0.01）. There was a significant positive correlation between the bone mineral density of the thoracic and lumbar vertebrae （for males， r = 0.96； for females， r = 0.98； P < 0.01）. Conclusion Both thoracic and lumbar QCT accurately displayed BMD and bone loss in different age groups， and thoracic QCT could be used as a method for evaluating and monitoring bone loss.