A Study of TACI-antibody Fusion Protein Injection (RC18) in Subjects With Primary Sjögren's Syndrome

Inclusion Criteria: * Voluntarily signed informed consent ; * Patient with primary Sjögren's syndrome according to the European - American consensus group criteria. * Seropositive at screening for anti-Ro/Sjögren's syndrome type A(SSA) antibodies * ESSDAI score ≥ 5. Exclusion Criteria: * Diagnosis of secondary Sjogren's syndrome, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and other autoimmune diseases; * Abnormal laboratory parameters need to be excluded, including but not limited to: * Immunosuppressive agents were used within 4 weeks prior to randomization.; * The use of hydroxychloroquine was allowed during the trial, and the pre-randomized drug regimen was stable for less than 12 weeks; * Use of biological agents for targeted therapy in the first 6 months of randomization; * Treatment of primary Sjogren's syndrome with traditional Chinese medicine and proprietary Chinese medicine within 4 weeks before randomization; * The use of saliva-stimulating drugs within 7 days prior to randomization; * Sodium hyaluronate eye drops, artificial tears can be used, and the stability time of the randomized pre-medication scheme is less than 4 weeks; * Intravenous immunoglobulin therapy or plasma exchange therapy within 6 months before randomization; * Infection with herpes zoster or HIV and hepatitis C virus(HCV) antibody positive; * Currently suffering from active hepatitis or severe liver lesions and history; * Malignant tumor patients ; * Combined with involvement of important organs or neuropathy; * Have participated in any clinical trial in the first 28 days of the initial screening or 5 times half-life period of the study compound (taking the time for the shorter). * Pregnant , lactating women and men or women who have birth plans during the research; * Investigator considers candidates not appropriating for the study