Inclusion Criteria:
* Pathologically confirmed, initially treated, surgically resectable head and neck squamous cell carcinoma.
* Clinical stage III to IVB (AJCC 8th edition), except HPV-positive oropharyngeal cancer
* Following multidisciplinary discussions involving otolaryngologists and radiation oncologists, the assessment concluded that the tumor is resectable or marginally resectable and suitable for preoperative SBRT
* Karnofsky Performance Status score ≥ 70
* Ages 18 to 70
* The primary organ functions meet the test requirements
* Patients participate voluntarily and sign informed consent forms
Exclusion Criteria:
* Patients previously treated with head and neck surgery were excluded from diagnostic biopsies of primary and regional lymph nodes
* Previous chemotherapy for any reason, or radiotherapy in the head and neck area, or molecular targeted drug therapy; Previously received anti-PD-1, anti-PD-L1, anti-PD-L2 and other drugs or drugs acting on another irritating or co-inhibitory T cell receptor (such as CTLA-4, OX 40, CD137) treatment, or cell biotherapy
* Pregnant or lactating women
* Have had or co-had other malignancies
* The patient also has a serious, uncontrolled illness
* Heart, brain, lung and other important organ function abnormal. Patients with hypertension (systolic blood pressure \>140 mmHg, diastolic blood pressure \>90 mmHg) who cannot be reduced to the normal range by antihypertensive drugs have grade I or above myocardial ischemia or myocardial infarction, arrhythmia, and grade II cardiac insufficiency; Abnormal coagulation function (INR \>1.5 or prothrombin time (PT) \> ULN+4 seconds or APTT \>1.5 ULN), have a tendency to bleed or are receiving thrombolytic or anticoagulant therapy; Have a definite bleeding tendency; Patients with positive urinary protein (urinary protein test 2+ or more, or 24-hour urinary protein quantification \>1.0g)
* Glucocorticoid therapy for 30 days prior to initial administration (prednisone equivalent dose \> 10mg daily); Have an active autoimmune disease that has required systemic treatment (i.e., disease-modulating drugs, corticosteroids, or immunosuppressive drugs) in the last 2 years
* History of non-infectious pneumonia requiring corticosteroid treatment within 1 year prior to the first dose administration or current presence of interstitial lung disease
* Active infections such as tuberculosis that require systemic treatment
* A known history of human immunodeficiency virus (HIV) infection (i.e. HIV 1/2 antibody positive)
* Untreated active hepatitis B; Note: Hepatitis B subjects who met the following criteria were also eligible for inclusion: HBV viral load must be \<1000 copies /ml (200 IU/ml) prior to initial dosing, and subjects should receive anti-HBV therapy to avoid viral reactivation throughout study chemotherapeutic therapy. Subjects with anti-HBC (+), HBsAg (-), anti-HBS (-) and HBV viral load (-) do not need to receive prophylactic anti-HBV therapy, but need to closely monitor viral reactivation. Active HCV-infected subjects (HCV antibody positive and HCV-RNA levels above the lower limit of detection)
* Patients who have a history of psychotropic substance abuse and cannot abstain or have mental disorders
* The investigator determines other circumstances that may affect the conduct of the clinical study and the determination of the study results
* While participating in another therapeutic clinical study
