This study will evaluate the efficacy, safety and PK/PD of ocrelizumab at each dose in combination with methotrexate（MTX）in patients with active rheumatoid arthritis (RA). The data from this study will also be compared with those from a clinical study of ocrelizumab in patients with active RA that was conducted in the U.S.

This study will evaluate the efficacy, safety and PK/PD of ocrelizumab at each dose in combination with MTX in patients with active RA. The data from this study will also be compared with those from a clinical study of ocrelizumab in patients with active RA that was conducted in the U.S.

Inclusion Criteria:

• Diagnosis of RA for ≧6 months according to the revised 1987 ACR criteria for the classification of RA.
• Adult patients, ≧20 years of age.
• Receiving methotrexate at a dose of 6 to 8mg/week（oral）for ≧12 weeks, with a stable dose for the last 4 weeks before treatment.
• Positive serum RF.

Exclusion Criteria:

• Rheumatic autoimmune disease other than RA, or Significant systemic involvement secondary to RA (including but not limited to vasculitis, pulmonary fibrosis, or Felty's syndrome).Patients with secondary Sjögren's syndrome or secondary limited cutaneous vasculitis with RA are eligible.
• Functional Class Ⅳ as defined by the ACR Classification of Functional Status in RA.
• History of or current inflammatory joint disease other than RA (e.g., gout, reactive arthritis, psoriatic arthritis, seronegative spondyloarthropathy, Lyme disease) or other systemic autoimmune disorder (e.g., systemic lupus erythematosus, inflammatory bowel disease, scleroderma, inflammatory myopathy, mixed connective tissue disease or other overlap syndrome).
• Any surgical procedure (except for minor surgeries requiring local or no anaesthesia and without any complications or sequelae) within 12 weeks prior to or planned within 24 weeks after baseline.