This study is a multicenter, randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy and safety of Yuxuebi tablet in treating night pain of Ankylosing Spondylitis.

Inclusion Criteria:

1. Ages 18-65, male or female
2. Confirmed diagnosis of Ankylosing Spondylitis
3. Syndrome of traditional Chinese medicine is blood stasis syndrome
4. ASDAS-CRP (Ankylosing Spondylitis Disease Activity Score)≥2.1
5. Visual analogue scale (VAS) for night pain≥4分
6. Maintained stable doses of Sulfasalazine, Methotrexate, Leflunomide, etc. for more than 1 month if treating with Slow-Acting Antirheumatic Drugs
7. Maintained stable doses of biologics for more than 3 month if treating with biologics
8. Not use Nonsteroidal Antiinflammatory Drugs within 2 weeks
9. Patients who have not participated in other clinical trials within 4 weeks
10. Written informed consent

Exclusion Criteria:

1. Pregnant or breastfeeding or who expecting to conceive
2. Psoriatic arthritis or Enteropathic arthritis
3. AS with iritis or uveitis
4. Abnormal liver function
5. Abnormal kidney function，high level of Creatinine
6. WBC (White Blood Cell)<3.0×10^9/L or with Hematological Disease
7. Patients with poor control of hypertension or diabetes
8. Acute or chronic infectious diseases
9. Severe arrhythmia
10. Patients with malignant tumors or with a history of malignant tumors
11. Drug allergy
12. Patients who had taken Yuxuebi tablet for more than 4 weeks with poor outcome
13. Patients who are treating with Traditional Chinese medicine for promoting blood circulation and removing blood stasis
14. Alcohol or drug abuse
15. Participants who are not suitable for clinical trial under doctors' consideration.