Effects of Nonsteroidal Anti-Inflammatory Drugs in Recurrence of Spondyloarthritis Patients After Remission

Inclusion Criteria: * Capable of giving informed consent and complying with the examination program of the protocol; * Participants with axial SpA fulfilling the Assessment of Spondyloarthritis international Society 2009 (ASAS) axial SpA classification criteria; * Participants must fulfill the criteria of maintaining remission of aSpA, defined as ASDAS\<1.3； * Participants must fulfill the criteria of remission of aSpA defined as ASDAS\<1.3，then continuous to evaluate every four weeks for three times and ASDAS\<1.3 each time. * Laboratory results must fulfill following requirements: Hb≥85g/L；3.5×109/L≤WBC Count ≤10×109/L；Platelet count ≥ Normal lower limit; Liver function (ALT、TBIL) ≤Twofold of normal upper limit; Renal function (SCr) ≤Normal upper limit; * The pregnancy test must be negative for women of childbearing age; Efficient contraception must be taken for both male and female participants during the trial period and within three months after the end of the trial. Exclusion Criteria: * Participants who previously have experienced allergic reactions to NSAIDs or sulfa-drugs; * Participants who are intolerant of NSAIDs; * Participants who are in active axSpA episodes; * Participants with previous or currant ulcers and/or gastrointestinal conditions or bleeding in three months * Participants who were in acute infection or acute attack of chronic infection during screening period; * At the time of screening, participants who were in the acute stage of acute infection or chronic infection, and if the acute infection had improved, they could be re-screened. * Participants who suffer from invasive fungal infections (e.g. histoplasma, coccidiosis's, candida, aspergillus, blastomyces, pneumocystis, etc.) within the first 6 months of screening; Or opportunistic bacterial infections (e.g. bacterial, viral or other infections, including Legionella and Listeria); * Participants with other autoimmune diseases which are expected to influence the evaluation of experimental medications, such as inflammatory enteritis, psoriasis, uveitis, etc. * Participants with previous or currant congestive heart failure, coronary heart disease, serious arrhythmia; * Participants with severe, progressive, uncontrolled vital organ and systematic disorders, and other conditions that are considered inappropriate to participate in this trial; * Participants with circumstances that may affect the compliance (e.g. prolonged travel or leave, planned relocation, mental illness, lack of motivation to participate, etc.).