This is a multi-center, open label, randomized clinical trial of etanercept and celecoxib alone/combined treatment in effectiveness and safety on active ankylosing spondylitis (AS). Subjects will be randomly assigned in a 1:1:1 ratio to one of the three groups (celexocib 200mg bid, etanercept 50mg qw, etanercept plus Celecoxib group) for 54 weeks. Primary endpoints are the magnetic resonance imaging (MRI) Spondyloarthritis Research Consortium of Canada (SPARCC) score of sacroiliac(SI) joint and spine, as well as the Assessment of SpondyloArthritis International Society (ASAS)20 response rate at 52 weeks.

A multi-center, open label, randomized clinical trial evaluating the effectiveness and safety of etanercept and celecoxib alone/combined treatment will be conducted on active ankylosing spondylitis (AS) patients. Disease activity is defined as fulfilling three aspects below: BASDAI ≥ 4 or ASDAS≥ 2.1；CRP>6 mg/L or ESR 28 mm/1st hour；more than 2 and less than 16 syndesmophyts between cervical spine and lumber spine detected by X-ray. All patients were randomly assigned in a 1:1:1 ratio to one of the three treatment groups：celecoxib 200mg bid，etanercept 50mg qw and combined therapy for 52 weeks. Primary endpoints are the magnetic resonance imaging (MRI) Spondyloarthritis Research Consortium of Canada (SPARCC) score of sacroiliac(SI) joint and spine, as well as the Assessment of SpondyloArthritis International Society (ASAS) 20 response rate at 52 weeks. Key secondary Endpoints include the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS), Spondyloarthritis Research Consortium of Canada (SPRACC) SI joint structural score (SSS), BASDAI, ASDAS, ASAS40, ASAS70 and ASAS5/6 response rate at 52 weeks.

Inclusion Criteria:

• 18 to 65 years
• Meet 1984 NewYork modified criteria for AS
• BASDAI≥4 or ASDAS score ≥ 2.1
• CRP>6 mg/L or ESR>28 mm/h
• Syndesmophyte quantity ≥2 and <16 of spine
• Sexually active women of childbearing potential must agree and commit to use a medically accepted form of contraception
• No active or latent tuberculosis infection.

Exclusion Criteria:

• Pregnant or breastfeeding women
• current or previous history of psoriasis or inflammatory bowel disease.
• infection with clinical significance within 24 weeks before screening
• receipt any bio-agents treatment within 12 weeks before screening
• corticosteroids intra-articular injections in last 3 months before the trial
• Significant concurrent medical events including: Gastrointestinal ulcer, myocardial infarction within 12 months before the screening visit, unstable angina pectoris, congestive heart failure.
• Alcohol and drug abuse