• Age: ≥ 18 years, male or female;

• Histologically confirmed squamous cell carcinoma of the head and neck (oral cavity, oropharynx, larynx, hypopharynx) (SCCHN);

• Recurrent/metastatic SCCHN not suitable for local treatment such as surgery or radiotherapy in the opinion of the investigator;

• At least one measurable tumor lesion according to RECIST 1.1 criteria;

• The tumor expresses PD-L1, with a comprehensive positive score CPS ≥ 1;

• Eastern Cooperative Oncology Group (ECOG) PS: 0-1

• Expected survival ≥ 3 months;

• Normal function of major organs, meeting the following criteria: blood routine examination criteria must be met: (no blood transfusion within 14 days before screening) 1) HB ≥ 90 g/L; 2) ANC ≥ 1.5 × 109/L; 3) PLT ≥ 75 × 109/L; biochemistry: (without transfusion or blood product within 14 days before screening) 1) BIL ≤ 1.5 × upper limit of normal (ULN) (≤ 3 × ULN for patients with Gilbert's syndrome); 2) ALT and AST ≤ 2.5 × ULN (≤ 5 × ULN for patients with liver metastasis); 3) Serum creatinine ≤ 1.5 × ULN or creatinine clearance ≥ 50ml/min (Cockcroft-Gault formula); 4) Coagulation function: activated partial thromboplastin time (APTT), international normalized ratio (INR), prothrombin time (PT) ≤ 1.5 × ULN; left ventricular ejection fraction (LVEF) ≥ 50% assessed by cardiac Doppler ultrasound;

• Women of childbearing potential must have a negative pregnancy test (serum or urine) within 14 days prior to enrollment and are willing to use reliable contraception during the trial and must be non-lactating patients; male subjects must use reliable contraception from the start of treatment to 6 months after the last dose;

• The subjects voluntarily join the study, sign the ICF, have good compliance, and cooperate in the follow-up