Intestinal radiation disease develops in about 1 week when the small intestine becomes critical. Acute radiation disease is a systemic disease caused by exposure of the body to large doses (>1Gy) of ionizing radiation in a short period of time. Acute radiation disease can occur with both external and internal irradiation, but external irradiation is the main cause. External radiation causes acute radiation sickness, such as gamma rays, neutrons and X-rays. Lymphocytes (mainly spleen and lymph nodes) are similar to bone marrow in terms of cell division inhibition, cell necrosis, reduction and hemorrhage, and develop faster than bone marrow and recover earlier than bone marrow, but complete recovery takes longer time. With the development of hematopoietic organ lesions, the clinical course of myeloid radiculopathy has obvious stages, which can be divided into initial, pseudo-healing, extreme and recovery stages. Especially, the moderate and severe stages are obvious.