A Study to Evaluate the Efficacy and Safety of SHR0302 in Patients With Rheumatoid Arthritis

Inclusion Criteria: * Provide signed informed consent. * RA diagnosis consistent with the 2010 ACR/EULAR criteria; * Moderate to severe RA defined by 6 or more tender joints, 6 or more swollen joints (68- or 66-joint count), and an ESR of 28 mm/h or greater or a CRP level greater than 5mg/L. * Subjects were required to have an inadequate response to treatment with csDMARDs before baseline. * If subjects are taking permitted csDMARDs or low-dose corticosteroid orally at baseline , the stable doses should have lasted for more than 4 weeks already. * BMI ≥18 kg/m2 Exclusion Criteria: * Pregnant women or refuse to receive contraception during the study. * Lab abnormality within 4 weeks of randomization as follows: WBC count \<3.0×10\^9/L；neutrophil count\<1.5×10\^9/L;hemoglobin level\<90.0 g/L ; platelet count \<100×10\^9/L; AST or ALT levels greater than the upper limit of normal; HBsAg or HCV or HIV antibody positivity. * History of another autoimmune rheumatic disease ; history of cancer or infection including tuberculosis and hepatitis; history of important cardiovascular events or thrombotic diseases. * Previous treatment with JAK inhibitor or cytotoxic drugs; bDMARDs within 6 months of randomization; other strong immunosuppressants within 3 months of randomization.