This study is intended to evaluate the efficacy and safety of Iguratimod Plus Methotrexate Compared to Leflunomid Plus Methotrexate in patients with active Rheumatoid Arthritis (RA).

Inclusion Criteria:

• Subjects with a diagnosis of RA according to the diagnostic criteria of the American College of Rheumatology (ACR) (revised in 1987)
• Rheumatoid Arthritis for more than 3 months from the time of the initial diagnosis
• Functional Class II-III
• Subjects have active RA at the time of screening
• Subjects with inadequate response to biologics should have a washout period before the initiation of study. For etanercept, washout period should be 2-week, and 8-week for infliximab and adalimumab.
• For firstly diagnostic RA patients, the disease activity should be moderate to severe, with DAS28>3.2
• Must have at least 4 tender joints (66 join count) and 8 swollen joints( 68 join count) at screening and baseline
• Has a C-reactive protein ≥ 10 mg/L(or 1.0 mg/dL) OR Erythrocyte Sedimentation Rate (ESR) ≥ 28 mm/hr
• Must have a negative Pregnancy test and use adequate method of contraception throughout the trial
• Written informed consent

Exclusion Criteria:

• Preceding treatment with DMARDs, immunosuppressants (cyclophosphamide, cyclosporine, azathioprine, etc.), or Tripterygium within 4 weeks prior to study entry
• Subjects have been treated with iguratimod or leflunomide combined with MTX before screening.
• Subjects combined with other autoimmune disease, such as systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD), scleriasis and polymyositis, except for Sjögren syndrome.
• Chest x-ray abnormalities, such as tuberculosis, interstitial pulmonary fibrosis, etc.
• ALT >1.5×ULN, AST >1.5×ULN, Cr >135umol/L, total bilirubin>1.5×ULN
• WBC<4×109/L，HGB<85g/L，PLT<100×109/L
• Subjects with serious cardiovascular, renal, hematologic, endocrine diseases or malignant
• Women of Pregnant or breastfeeding, and male or female with recent plan to conception
• Subjects with immunodeficiency, uncontrolled infection and active gastrointestinal disease
• Allergic to any of the study drugs
• History of alcoholism
• Subjects with mental illness
• Subjects receiving live vaccines recently
• Subjects participating in other clinical study within 3 months prior to study entry