Inclusion Criteria:  (1) Histology confirmed as anal canal squamous carcinoma;  Clinical stage I-III No distant metastasis; Age: 18-75 years old; ECOG 0-1 score Adequate bone marrow, liver, kidney function if HIV infected, HIV loading is below the lower limit (<20 copy </ ml), with the number of CD4+T cells > 300> ml Non-pregnant or lactating women; No other malignant disease within 5 years before diagnosis of anal cancer squamous carcinoma (except endocervical cancer in situ or skin basal cell carcinoma which had been cured); no other malignant disease beside anal cancer squamous carcinoma No other serious disease leading to shortened survival. No previous anal canal surgery or anal tumor resection (except for biopsy); No chemotherapy received within the previous 5 years; No previous pelvic radiation; No biological treatment received in the previous 5 years; No previous immunotherapy received.  Exclusion Criteria:  Diagnosed as stage I and well differentiated squamous cell carcinoma Distant metastasis Received radiation therapy in abdominal or pelvic regions Pregnant, lactating woman patient or fertile but lacks adequate contraceptives Infectious disease: Active phase chronic hepatitis B or hepatitis C (high copies of virus DNA); Other serious active clinical infection Patients with active tuberculosis (TB) are receiving anti-tuberculosis treatment or have received anti-tuberculosis treatment within 1 year before screening; Chronic inflammatory colorectal disease, unrelieved ileus Dyscrasia or organ decompensation Allergic to research-related drugs Severe hypertension with poor drug control; Epilepsy require medical treatment (such as steroid or antiepileptic therapy); Drug abuse and medical, psychological or social factors that may interfere with patients' participation in the study or affect the evaluation of the study; Patients have any active autoimmune diseases or a history of autoimmune diseases (including but not limited to: interstitial pneumonia, uveitis, enteritis, hepatitis, hypophysitis, nephritis, hyperthyroidism and decreased thyroid function; patients with vitiligo or with complete remission of asthma in childhood and without any intervention in adulthood may be included; patients with asthma requiring bronchodilators intervention are not included. Received any anti-infection vaccine (e.g. influenza vaccine, chickenpox vaccine, etc.) within 4 weeks before enrollment; Complications require long-term treatment with immunosuppressive drugs, or requiring systemic or local use of immunosuppressive corticosteroids(>10mg/day prednisone or other therapeutic hormones); Any unstable condition or which endangers the patients' safety and compliance; Refuses to sign informed consent