Inclusion Criteria:  A biopsy proven histological diagnosis of rectal adenocarcinoma； An ARMS-PCR proven KRAS, NRAS mutation, excluding BRAF mutation or microsatellite instablility-High; No intestinal obstruction, distant metastasis was excluded by CT, MRI or PET / CT; MRI proven T3c-T4, CRM positive, N2, extramural vascular invasion positive or lateral lymph node positive of locally advanced rectal cancer; Age between 18-75 years; ECOG (Eastern US Cooperative Oncology Group) score: 0-1;  Has sufficient organ function:  Hemopoietic function: hemoglobin ≥ 90 g / L, platelet ≥ 80 g / L × 109 / L, neutrophils ≥ 1.5 × 109/L Liver function: ALT and AST < 2.5 × ULN; Renal function: serum creatinine < 1.5 ULN; Willing to participate and informed consent signed；  Exclusion Criteria:  An ARMS-PCR proven RAS wild type, BRAF mutation and microsatellite instablility-High; Patients having undergone chemotherapy, radiotherapy or surgery for colorectal cancer; Patients with other uncontrolled malignant tumors (except early-stage basal cell carcinoma or cervical carcinoma in situ) ; Female patients who are pregnant or breastfeeding; Patients with severe heart, liver, or kidney, or neurological or psychiatric disease; Patients with active infection; Poor overall health status, ECOG ≥ 2; Patients with concomitant diseases that seriously endanger the safety of patients or affect the completion of the study in the judgment of the investigator; Known hypersensitivity reactions to any investigational drugs;