Subacute combined degeneration of the spinal cord has a clear etiology, mainly due to vitamin B12 intake, absorption, binding, transportation or metabolic disorders, resulting in insufficient levels of vitamin B12 in the body, which causes degenerative diseases of the central and peripheral nervous system, the lesions mainly affect the anatomical structures such as posterior cords of the spinal cord, lateral cords, peripheral nerves and other anatomical structures. Clinical manifestations mainly manifested in the double lower limbs deep sensory impairment, lack of, thus appearing sensory ataxia, or even spastic paralysis, and peripheral neuropathy manifestations, usually accompanied by the clinical manifestations of anemia. The core cause of the disease is vitamin B12 deficiency, because vitamin B12 is an essential coenzyme for DNA and RNA synthesis, and an essential substance for maintaining the structure and function of myelin sheaths. A deficiency of vitamin B12 will lead to insufficient synthesis of nuclear proteins, thus affecting the methylation of CNS, resulting in loss of myelin sheaths, degeneration and disease. Vitamin B12 is also involved in the synthesis of hemoglobin, so the patient will also be accompanied by anemia, even pernicious anemia clinical manifestations. Once the above clinical manifestations occur, the patient should go to the Department of Neurology for comprehensive diagnosis and treatment.