Objective:To analyze the correlation between paraspinal muscle parameters and the angle of degenerative thoracolumbar segmental kyphosis.Methods:From November 2021 to April 2023, a total of 90 female patients with lumbar degenerative disease who underwent surgical treatment in the Department of Spine Surgery, Beijing Jishuitan Hospital were retrospectively analyzed. The average age was 67.62±4.98 years (range, 60-80 years), and the average height was 1.58±0.05 m (range, 1.48-1.70 m). Weight 63.79±9.13 kg (range, 47-90 kg), body mass index 25.48±3.35 kg/m 2 (range, 18.37-36.05 kg/m 2). The angle of kyphosis of the thoracolumbar segments was 6.65°±10.38° (range, -17.34° to 9.34°). Disease diagnosis: 32 cases of lumbar disc herniation and 58 cases of lumbar spinal stenosis. Frontal and lateral radiographs of the thoracolumbar segments in the standing position were taken to measure the angle of kyphosis of the thoracolumbar segments; quantitative CT of the thoracolumbar segments and Osirix software were used to measure the parameters of the paravertebral muscles at the levels of T 12, L 3, and L 5, including paravertebral muscle cross-sectional area, skeletal muscle area, and tissue density, the proportion of fat infiltration, and the height-corrected skeletal muscle area index. The correlation between paraspinal muscle parameters and the angle of thoracolumbar segmental kyphosis was analyzed, and the factors affecting the angle of thoracolumbar segmental kyphosis were analyzed using multiple linear regression. Results:Correlation analysis showed a negative correlation between the angle of thoracolumbar segmental kyphosis and the tissue density of T 12 skeletal muscle ( r=-0.303, P=0.004) and L 5 skeletal muscle ( r=-0.219, P=0.038). Age was negatively correlated with T 12 skeletal muscle tissue density ( r=-0.263, P=0.012), T 12 height-corrected skeletal muscle area index ( r=-0.221, P=0.036), T 12 paravertebral muscle cross-sectional area ( r=-0.280, P=0.007), L 3 skeletal muscle tissue density ( r=-0.266, P=0.011) and L 5 skeletal muscle tissue density ( r=-0.290, P=0.006). There was no correlation between bone mineral density and paravertebral muscle parameters ( P>0.05). Multiple linear regression showed that T 12 skeletal muscle tissue density ( β=-1.125, P<0.001), T 12 fat-infiltrated proportion ( β=-0.849, P=0.001), L 3 skeletal muscle tissue density ( β=0.996, P<0.001), and L 3 fat-infiltrated proportion ( β=0.496, P=0.020) were independent factors influencing the angle of thoracolumbar segmental kyphosis . Conclusion:T 12 and L 3 paraspinal muscle density and fat-infiltrated proportion are independent factors affecting the angle of thoracolumbar kyphosis. The smaller the density and fat-infiltrated proportion of T 12 paraspinal muscle, and the larger the density and fat-infiltrated proportion of L 3 paraspinal muscle, the larger the angle of thoracolumbar kyphosis.