Objective:To explore the value of quantitative parameters of cortical and cancellous bone in the first lumbar vertebrae (L1) based on CT spinal bone quantification system for evaluating the severity of chronic obstructive pulmonary disease (COPD) in males.Methods:A total of 88 male patients with COPD diagnosed at the Second Affiliated Hospital of Shandong First Medical University from August 2021 to December 2022 were retrospectively analyzed. According to the 2023 edition of global initiative for chronic obstructive lung disease (GOLD), the patients were classified as GOLD Ⅰ (29 cases), GOLD Ⅱ (36 cases), and GOLD Ⅲ-Ⅳ (23 cases). And then 29 males with normal lung function during the same period were recruited. People with normal lung function and COPD patients of GOLD Ⅰ-Ⅱ were classified as non-severe COPD group (94 cases), COPD patients of GOLD Ⅲ-Ⅳ were classified into the severe COPD group (23 cases). On the CT images of L1, the CT spine bone quantification system was used to automatically segment cortical and cancellous bone. The total volume, cortical volume, cancellous volume, average cortical thickness, cortical bone average CT value and cancellous bone average CT value of L1 vertebral body were measured using the system respectively. Single factor analysis of variance was used to compare the differences of various parameters among normal lung function and COPD patients with different lung function grades. The efficacy of various parameters in evaluating the severity of COPD were calculated using the receiver operating characteristic curve.Results:The overall differences in L1 vertebral total volume, cancellous volume and cortical bone average CT value among people with normal lung function and COPD patients of GOLD Ⅰ, Ⅱ, and Ⅲ-Ⅳ were statistically significant ( F=3.60, 4.26, 5.39, P=0.016, 0.007, 0.002), and showed a downward trend as the severity of COPD progressed. There were no statistically significant difference in cortical volume, average cortical thickness and cancellous bone average CT value of L1 ( P>0.05). The area under the curve (AUC) for distinguishing severe and non-severe COPD was 0.64 (95%CI 0.54-0.72), 0.65 (95%CI 0.56-0.74) and 0.75 (95%CI 0.66-0.83) for the total vertebral volume, cancellous volume and cortical bone average CT value of L1 respectively. The AUC of cortical bone average CT value was the highest, with a cutoff value of 217 HU/mm 3, a sensitivity of 69.6% and a specificity of 80.9%. Conclusion:Male COPD patients have reduced bone mass compared to the same age male population. The L1 quantitative parameters measured based on the CT spinal bone quantification system can effectively evaluate the severity of lung function in male COPD patients. Among them, the cortical bone average CT value has the highest diagnostic efficacy.