In this phase I single-arm clinical study, 20 patients with T4b unresectable locally advanced colon cancer are proposed to be enrolled, who will be treated with MR-Linac with short course radiotherapy (25Gy/5F), followed by 4 cycles of mFOLFOX6 or 3 cycles of XELOX chemotherapy, then radical surgical resection, and then postoperatively with 8 cycles of mFOLFOX6 or 5 cycles of XELOX. The study will assess patients' surgical R0 resection rate, pCR or cCR rate, PFS, OS, and related adverse effects of treatment, aiming to explore the feasibility, safety, and efficacy of MR-Linac in the treatment of unresectable locally advanced colon cancer.