A Study to Evaluate the Efficacy and Safety of Sintilimab in Combination With IBI305 (Anti-VEGF Monoclonal Antibody) Compared to Sorafenib as the First-Line Treatment for Advanced Hepatocellular Carcinoma.

Inclusion Criteria: 1. Hepatocellular carcinoma confirmed by histology/cytology. Cirrhosis meets the clinical diagnostic criteria for hepatocellular carcinoma of the American Association for the Diagnosis of Liver Diseases (AASLD). 2. ECOG performance status between 0 and 1 3. No systematic anti-tumor treatment has been performed.(End of postoperative adjuvant chemotherapy for more than 6 months allowed). 4. Barcelona Clinic Liver Cancer stage C. BCLC stage B, not suitable for radical surgery and/or local treatment. 5. At least 1 lesion with measurable disease at baseline by RECIST V1.1. 6. Child-Pugh: \<=7 7. Adequate organ and bone marrow function. Exclusion Criteria: 1. With fibrous lamellar hepatocellular carcinoma, sarcomatoid hepatocellular carcinoma, cholangiocarcinoma components in tumor tissues. 2. Have a history of hepatic encephalopathy or have a history of liver transplantation. 3. With clinical symptoms requires drainage of pleural effusion, ascites or pericardial effusion. 4. Central nervous system (CNS) metastasis. 5. Uncontrolled high blood pressure, systolic blood pressure \>140mmHg or diastolic blood pressure \>90mmHg after optimal medical treatment. 6. Local treatment for liver lesions within 4 weeks.