Objective:To observe the long-term effects of conventional disease modifying anti-rheumatic drugs (cDMARDs) in the treatment of ankylosing spondylitis (AS) and drug-related adverse reactions, and provide reference to clinical treatment and assessment.Methods:Retrospective analysis was performed for AS patients with more than 10 years follow-up records in the Department of Rheumatology and Immunology, Peking University Shenzhen Hospital. The AS patients enrolled were treated with cDMARDs, non-steroid anti-inflammatory Drugs (NSAIDs), and glucocorticoidsonl only. The treatment group was treated continuously for at least 3 years, and the control group was untreated or treated for less than 3 months. Clinical symptoms, inflammatory indicators, imaging results and drug-related adverse reactions of all patients were collected for statistical analysis. The counting data were tested by χ2 test, the measurement data in normal distribution was tested by t test, and the measurement data that not normally distributed was tested by mann-whitney U test. Paired test was used for statistical processing before and after treatment. Results:A total of 166 eligible patients were included, including 111 in the treatment group and 55 in the control group. There were no statistical significant differences between the treatment group and the control group at baseline including the mean follow-up time, symptomatic disease course, age, sex ratio, human lymphocyte antigen (HLA)-B27 positive rate, duration of morning stiffness, pain at night, peripheral arthritis, ESR, CRP and imaging data. After 10 years, the treat-ment group had shorter morning stiffness[(8±18) vs (22±34), U=2 228, P=0.008], less nocturnal pain [(2/1.9%) vs (19/36.5%), χ2=37.037, P<0.01], lower ESR level [(14±13) vs (20±19), t=2.249, P=0.026], lower CRP level [(6±6) vs (10±11), t=2.154, P=0.033], lower incidence of peripheral arthritis [(23/20.7%) vs(25/45.5%), χ2=10.946, P=0.001] and lower sacroiliac arthritis progression rate [(28/25.2% ) vs (46/83.6%), χ2=50.922, P<0.01], and lower spinal progression rate [(8/7.2%) vs (51/92.7%), χ2=117.407, P<0.01] compared with the control group. The differences between the two groups was statistically significant. The main medications and drug proportions in the treatment group were as follows: sulfasalazine (100%), methotrexate (86.5%), NSAIDs (98.2%), glucocorticoid (78.4%) and thalidomide (62.2%). The main drug-related adverse reactions that occurred during the treatment included dizziness, abnormal menstruation, and reversible liver dysfunction. Conclusion:The combination of cDMARDs can effectively control the clinical symptoms of most AS patients, reduce inflammation indicators, delay the progression of sacroiliac joint and spinal damage, and have no serious drug-related adverse reactions. Almost all of the untreated AS patients have radiographic progression of the sacroiliac joint and spine.