Abstract: Objective: To evaluate the efficacy and safety of recombinant human tumor necrosis factor receptor,Fc fusion protein,in treating ankylosing spondylitis（AS）. Methods: This was a randomized,double-blind,placebo-controlled trial in the first 6 weeks and an open labeled trial in the next 6 weeks.52 patients of active AS were randomly assigned to receive twice weekly subcutaneous injections of etanercept（25mg） or placebo for 6 weeks.The primary endpoint was proportion of ASAS20 responders at week 6.The secondary endpoints were the proportion of subjects achieving an ASAS50,ASAS70 and BASDAI50 improvement at week 6.Other secondary endpoints,related to reduced signs and symptoms of AS and improved range of motion and physical function were evaluated. Results: Treatment with etanercept resulted in significant improvement.At week 6,80% of patients in the etanercept group responded to the treatment as compared with 31% of those in the placebo group（P＜0.001）.Improvement over baseline values for other measures of disease activity was significantly greater in the etanercept group.Etanercept was well tolerated.The most frequent adverse event related to treatment was injection site reaction. Conclusion: Etanercept has demonstrated consistent evidence of efficacy and has been well tolerated by patients in the treatment of active AS.