Assess the Efficacy of Radiotherapy and Sequential Chemotherapy and AK104 Before TME Surgery for Local CRC（AK104-IIT-13） (AK104-IIT-13)

Inclusion Criteria: 1. Age 18-75 years old, gender is not limited; 2. Stage II/III under MRI or endoscopic ultrasound ; 3. Fiber colonoscopy or diagnosis examination, the lower boundary of the lesion is 15m ≤ from the margin; 4. Rectal adenocarcinoma confirmed or revisited by pathology; 5. Karl Fischer score ≥ 80 points or ECOG score of 0-1; 6. Meet the following laboratory diagnostic indicators: hemoglobin ≥ 100g/L, white blood cell ≥ 3.5×109/L; neutrophils≥ 1.5×109/L, platelet ≥ 100×109/L; creatinine ≤ 1.0× upper limit of normal (UNL), urea nitrogen (BUN) ≤ 1.0× upper limit of normal (UNL); Alanine aminotransferase (ALT) ≤1.5× upper limit of normal (UNL); Aspartate aminotransferase (AST) ≤1.5× upper limit of normal (UNL); Alkaline phosphatase (ALP) ≤1.5× upper limit of normal (UNL); Total bilirubin (TBIL) ≤ 1.5× upper limit of normal (UNL); urine protein (-); Clotting time is normal. 7. No history of allergy to 5-Fu drugs, no history of allergy to platinum drugs; 8. With primary rectal cancer required to undergo surgery (except palliative ostomy), chemotherapy or other anti-tumor therapy before diagnosis to enrollment; 9. Not received radiation before; 10. Sign the informed consent form. Exclusion Criteria: 1. Previous anti-PD-1/L1 and anti-CTLA-4 immune drugs or other immunoassay drugs; 2. With severe autoimmune diseases: active inflammatory bowel disease (including Crohn's disease, ulcerative colitis), rheumatoid arthritis, scleroderma, systemic lupus erythematosus, autoimmune vasculitis (such as Wegener's granulomatosis), etc.; 3. Symptomatic interstitial lung disease or active infection/non-infectious pneumonia; 4. Patients have risk factors for intestinal perforation: active diverticulitis, intra-abdominal abscess, gastrointestinal (GI) obstruction, abdominal cancer or other known risk factors for intestinal perforation; 5. History of other malignant tumors, excluding curable non-melanogenic skin cancer and carcinoma in situ of the cervix; 6. Active infection, heart failure, myocardial infarction, unstable angina or unstable arrhythmia within 6 months; 7. Physical examination or clinical laboratory findings that the investigator believes may interfere with the results or increase the patient's risk of treatment complications, or other uncontrollable diseases; 8. Breastfeeding or pregnant women; 9. Congenital or acquired immunodeficiency diseases including human immunodeficiency virus (HIV), or organ transplantation, allogeneic stem cell transplantation; 10. Known active hepatitis B virus (HBV), hepatitis C virus (HCV), active tuberculosis infection; 11. Vaccinated against tumors, or received other vaccines within 4 weeks before starting treatment (Note: Because the seasonal influenza vaccine for injection is mostly an inactivated vaccine, it is allowed to be vaccinated, while intranasal preparations are usually live attenuated vaccines, so it is not allowed) 12. Use other immunological agents, chemotherapy drugs, drugs in other clinical studies, and long-term cortisol therapy are not enrolled 13. With mental illness, substance abuse, and social problems that affect compliance will not be enrolled after a doctor's review 14. Allergic or contraindicated to the treatment of drugs.