This study aims to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of multiple ascending doses of IBI355 in primary Sjogren's syndrome (pSS) patients. This study also aims to evaluate the anti-Drug antibody after multiple ascending doses of IBI355 in pSS patients.

Inclusion Criteria:

1. Understand and sign the informed consent form;
2. Age ≥ 18 years, male or female；
3. Body Mass Index (BMI) within the range of 18.0 to 28.0 kg/m² (inclusive);
4. Meet the 2016 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria for Sjögren's Syndrome;
5. Positive for anti-Sjögren's syndrome A autoantibodies (SSA) and/or anti-Sjögren's syndrome B autoantibodies (SSB);
6. Unstimulated whole salivary flow rate > 0 ml/min;

Exclusion Criteria:

1. Individuals who have had allergic reactions to any components of IBI355, have allergic diseases, or possess an allergic constitution;
2. Those who cannot tolerate frequent venipuncture procedures;
3. Participants diagnosed with secondary Sjögren's syndrome, or whose clinical symptoms (or laboratory abnormalities) require explanation by another connective tissue disease (such as systemic lupus erythematosus, mixed connective tissue disease, etc.).
4. Subjects paticipated in the other clinical trail in 1 month or less than 5 t1/2 since the previous clinical trial (which is longer)；
5. Subjects with an infection requiring systemic medication was present within 30 days prior to randomization;
6. HIV-Ab、RPR、HCV-Ab、HBV、HBeAg or HBcAb, one of them positive;
7. There have a clinical or imaging evidence that the subject with active tuberculosis, or there is evidence that the subject is in the incubation period for tuberculosis;

6.Patients with a history of central nervous system, cardiovascular system, digestive system, respiratory system, urinary system, blood system, metabolic disorders and other systemic diseases; 7. Subject with a hcg positive; 8.Patients with a history of neuropsychiatry or who are considered unfit to participate in this clinical trial; 9.Patients with pulmonary interstitial fibrosis, or those requiring combined antifibrotic drug therapy, or those with abnormal lung function that the investigators determined was not suitable for this study; 10. Need to use other drugs that could cause xerostomia during the study.