Inclusion Criteria:  informed consent was signed ; Age 18-75; Pathologically confirmed rectal adenocarcinoma, colonoscopy,MRI, CT and other examinations confirmed that the tumor was located under peritoneal reflexion, clinical staging was T1-4N1-2M0, pelvic MRI evaluation showed at least one lateral lymph node with short diameter ≥5 mm; Pelvic MRI was evaluated no more than 14 days before enrollment; ECOG 0-2 points; No prior history of other malignant tumors, except for cured basal cell carcinoma of the skin and carcinoma in situ of the cervix.  Exclusion Criteria:  Previous radiotherapy or surgical treatment for colorectal cancer (except biopsy for pathology); Whole body CT, MR or PET-CT (including at least chest, whole abdomen, and pelvis) confirmed distant metastasis (M1); Previous or coexisting active malignancies (other than malignant neoplasms that have received curable treatment and have not been present for more than 3 years or carcinoma in situ that can be cured by adequate treatment); Receiving major operations such as laparotomy, thoracotomy, laparoscopic resection of organs or serious external injuries within the previous 4 weeks; Active coronary artery disease, severe/unstable angina pectoris or newly diagnosed angina or myocardial infarction within the 12 months prior to study participation; Patients who have experienced thrombosis or embolism within the past 6 months have received radiotherapy or surgical treatment for rectal cancer (except biopsy for pathology) New York Heart Society (NYHA) Grade II or higher congestive heart failure; The presence of CTCAE grade 2 or above toxicity (except anemia, alopecia, and skin pigmentation) due to any previous treatment that has not resolved; Pregnant or lactating women; Accompany with any medical condition that would affect patient safety and study compliance; Patients determined by the investigator to be unsuitable for participation in this clinical trial.