Inclusion Criteria:  NMOSD as defined by either of the following 2015 criteria with anti-AQP4 antibody (Ab) seropositive status at screening Clinical evidence of at least 1 documented relapse in last 12 months prior to screening Expanded Disability Status Scale (EDSS) score from 0 to 7.5 inclusive at screening Age 18 to 70 years, inclusive at the time of informed consent  Exclusion Criteria:  Any previous treatment with anti-CD20, eculizumab, anti-BLyS monoclonal antibody (e.g., belimumab), any other treatment for prevention of multiple sclerosis (MS) relapse (e.g., interferon, natalizumab, glatiramer acetate, fingolimod, teriflunomide or dimethyl fumarate) within 6 months prior to baseline. Received immunosuppression such as azathioprine, mycophenolate mofetil, methotrexate, cyclophosphamide, tacrolimus, mitoxantrone, cyclosporine A, etc, and rug therapy, biological agents such as satralizumab, tocilizumab, eculizumab, etc, 3 months prior to the first administration. Evidence of serious uncontrolled concomitant diseases that may preclude participant participation, as described; Other nervous system disease, cardiovascular disease, hematologic/hematopoiesis disease, respiratory disease, muscular disease, endocrine disease, renal/urologic disease, digestive system disease, congenital or acquired severe immunodeficiency. Known active infection within 3 months prior to baseline Pregnancy or lactation. History of severe allergic reaction to a biologic agent Evidence of chronic active hepatitis B or C Evidence of active tuberculosis  Following laboratory abnormalities at screening*:  White blood cells (WBC) <4.0 x10^3/microliter (μL) Absolute neutrophil count (ANC) <2.0 x10^3/μL Absolute lymphocyte count <0.5 x10^3/μL Platelet count <80 x 10^9/ L Aspartate aminotransferase (AST) or alanine aminotransferase History of drug or alcohol abuse within 6 months prior to baseline Receipt of any live or live attenuated vaccine within 4 weeks prior to baseline Uncontrolled systemic diseases, including hypertension that cannot be effectively controlled after treatment (systolic blood pressure ≥150 mmHg and/or diastolic blood pressure ≥100 mmHg), diabetes, gastrointestinal diseases, etc.; or the investigator believes that there is anything inappropriate reasons for selection.