Efficacy and Safety of TAF for 48 Weeks in HBeAg Positive CHB Patients

common criteria: * Age 18-70 years old (including both ends), male or female, chronic HBV infection (HBsAg positive for more than 6 months, or liver biopsy results show chronic hepatitis B infection) * HBsAg positive * Patient must be capable of understanding and signing written informed consent; Before commencing the study procedure, participants must obtain informed consent. * Lifestyle requirements: All subjects considered by the investigator to be sexually active and capable of becoming pregnant or making sexual partner become pregnant must agree to use an effective contraceptive method for the entire study period (from the signing of the informed consent to at least 28 days after the last dose of the investigational drug was administered). Addition criteria: Treatment naive patients * HBV DNA\> 2×104 IU/ml * ALT\>2×ULN；or ALT\>1×ULN，but liver biopsy showed inflammation greater than or equal to G2, or/and liver fibrosis greater than or equal to S2 * No treatment with NA or/or αIFN within 1 year ETV treatment experienced patients * ETV treatment for 1 to 2 years before * HBsAg\>3000IU/mL * HBV DNA\<20IU/mL * ALT\<1×ULN * No other NA therapy prior to entecavir treatment * Patients had a desire to convert to TAF therapy Exclusion Criteria: Treatment naive patients * treated with NA or/or αIFN within 1 year * Pregnant women, lactating women, or women who plan to become pregnant within 2 years * Co-infection with Hepatitis C, Hepatitis D or HIV; * Chronic liver diseases with non-HBV etiology (including but not limited to: autoimmune hepatitis, primary biliary cirrhosis, primary cirrhosis cholangitis, hemochromatosis, etc. * There is evidence of Child-Pugh grade C decompensated liver disease, or moderate to severe ascites, and grade III-IV hepatic encephalopathy * There are symptoms and signs of hepatocellular carcinoma. If screening for alpha-fetoprotein (AFP) \<50 ng / mL, imaging examination are not required; but if screening for AFP\> 50 ng / mL, imaging examination are required * current alcohol or drug abuse may affect compliance * Patients who recieved solid organ or bone marrow transplantation. Liver or kidney transplantation patients can be enrolled * malignant tumors within 5 years. Patients being evaluated for possible malignant tumors should be excluded * Study drugs were used within 3 months prior to screening * Patients who are participating in other clinical trials, or have been treated with the study drugs within 12 weeks before screening * Inability or unwillingness to provide informed consent or non-compliance with research requirements * Patients who are unwilling to purchase TAF on their own * In addition to the above exclusion criteria, patients who meet any of the contraindications listed in the label of the investigational drug product ETV treatment experienced patients ●Patients who had received IFN and/or other NA (except entecavir) within 1 year Other exclusion criteria were as same as 2-13 of the exclusion criteria for treatment naive patients.