This is a prospective, open-labled, randomized controlled study to assess efficacy and safety of treatment with Sintilimab (PD-1 antibody) combined Peg-IFNα-2b in CHB patients on stable NAs treatment.

Inclusion Criteria:

1. 18 - 65 years old;
2. Chronic hepatitis B patients with clear diagnosis of hematology, etiology and clinical (for example: HBsAg positive for more than 6 months);
3. Treatment with NAs (ETV, TDF or TAF）at least 1 years and continue NAs therapy during screening;
4. HBV DNA and HBeAg turn negative after NAs treatment;
5. HBsAg ranged 200-1000 IU/ml.

Exclusion Criteria:

1. Cirrhosis;
2. platelet count < 90×10^9/L, WBC count < 3.0×10^9/L, neutrophil count < 1.3×10^9/L, ALT > ULN（40U/L）, total bilirubin > 2ULN;
3. History of or suspicion of hepatocellular carcinoma
4. Patients received interferon therapy within 12 months;
5. Patients received immunosuppressive therapy or other therapy influenced study within 12 months;
6. Hepatitis A, hepatitis C, hepatitis D, HIV infection or other active infections;
7. Alcohol or drug abuse/dependence;
8. Investigator judges that the participants are not suitable for this study.