Inclusion Criteria:  Has unresectable Stage III or Stage IV or melanoma per American Joint Committee on Cancer (AJCC) staging system version 8. At least one measurable lesion conforming to RECIST 1.1 criteria. No previously received systematic therapy. The toxicity of prior treatment has recovered to ≤1 grade according to CTCAE 5.0. ECOG score 0-1. The expected survival time is ≥ 12 weeks. Adequate organ and bone marrow function. Female subjects of childbearing age must undergo a serum pregnancy test within 7 days before the commencement of the study and the results are negative, and are willing to use a medically approved high potency contraceptive method during the study period and within 3 months after the last administration of the study drug; For male subjects whose partner is a female of childbearing age, they should be surgically sterilized or agree to use an effective method of contraception during the study period and for 3 months after administration of the last study. Willing to consent and signed the informed consent, and able comply with the planned visit, research treatment, laboratory examination and other test procedures.  Exclusion Criteria:  History of other malignant tumors, except for cured skin basal cell carcinoma, squamous cell carcinoma of skin, superficial bladder carcinoma, papillary thyroid carcinoma, intraductal carcinoma and cervical carcinoma in situ. Has ocular melanoma. The first study drug treatment was less than 4 weeks from the last systematic antitumor therapy or 5 half-lives from the last targeted therapy; less than 4 weeks from major surgery; less than7 days from immunosuppressive drug; less than 3 weeks from immunomodulatory; less than 4 weeks from live attenuated vaccine. Systemic antibiotic use for 7 days within 4 weeks prior to initial administration, or unexplained fever during screening/prior to initial administration. With active autoimmune disease or a history of autoimmune disease. With history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation. With immunodeficiency, eg HIV, HBV, HCV. Have a clear history of serious and uncontrolled other disease or mental disorders. Has a bleeding tendency or abnormal clotting function. Subjects with central nervous system disease or brain metastases. Known to be allergic to the active ingredients or excipients in this study. Other situations that the researcher considers inappropriate to participate in the research.