Objective To analyze the imaging changes of ankylosing spondylitis (AS) before and after the treatment of biologics combined with leflunomide. Methods A total of 30 cases of patients with active AS from October 2015 to September 2016 in our outpatient department and ward were selected and all given the treatment of biologics combined with leflunomide. The clinical and MRI follow-up review were performed before and after treatment for six months.The results of MRI and clinical efficacy were compared and the evaluation value of MRI was analyzed. Results The MR imaging features of 30 cases of ankylosing spondylitis before treatment is joint effusion(accounting for 86.67%), bone marrow edema(accounting for 73.33%), cartilage destruction(accounting for 53.33%), bone marrow fat deposition(accounting for 46.67%). After treatment, the MRI showed sacroiliac joint space effusion disappeared(20.00%) or reduction(43.33%), the degree and depth of bone edema with 53.33% reduction, the bone marrow fat deposition with 33.33% obvious decrease, the cartilage destruction with 16.67% unconspicuous changes, the cartilage damage of varying degrees with 13.33% increase. The sensitivity, specificity and accuracy of curative efficacy assessed by MRI scan were 95.83%, 66.67% and 90.00% respectively. The diagnostic consistency test was K=0.83, P<0.05, that is, the MRI imaging evaluation of clinical efficacy and clinical curative effect is consistent with each other. Conclusion Biologics combined with leflunomide are effective in the treatment of AS. MRI can clearly show the condition of joint lesions before and after treatment, and evaluate the therapeutic effect, which can meet the needs of follow-up review.