Objective To observe the effect of modified Qianghuo Shengshi decoction on spinal function and acute phase reactants in patients with ankylosing spondylitis. Methods A total of 84 patients with ankylosing spondylitis were divided into two groups：42 cases in the treatment group and 42 cases in the control group，respec⁃ tively. The control group was treated with conventional western medicine，while the treatment group was given con⁃ ventional western medicine combined with modified Qianghuo Shengshi decoction. Evaluate the clinical efficacy， and the TCM syndrome scores，the score of BASFI，the score of BASDAI，the score of BASMI，the main clinical indicators and acute phase reactants，Quality of life scale（SF⁃36）of the two groups were compared before and after treatment. Adverse reactions were compared. Results The total effective rate of the treatment group after treatment was 95.24%，compared to 71.43 % in the control group，was statistically significant differences（P < 0.05）； The TCM syndrome score，and the ESR and CRP levels，and the BASDAI，BASFI and basmi scores，the finger ground distance，the occipital wall distance and morning stiffness time of the treatment group were lower than those of the control group，while the thoracic mobility，Schober test and SF⁃36 score were higher than those of the control group（P < 0.05）；The adverse reactions of the treatment group was 4.76%，which was 19.05% in the control group，with statistically significant（P < 0.05）. Conclusion Qianghuo Shengshi decoction combined with western medicine is effective in the treatment of ankylosing spondylitis，which is related to the reduction of ESR and CRP levels.