S100 protein is an acidic calcium-binding protein found in astrocytes of the central nervous system. When damage occurs in the central nervous system, S100 protein is elevated in both cerebrospinal fluid and blood, and can be used for the detection of certain diseases as well as prognostic judgment. In clinical practice, it is mainly used in the following diseases: 1. Acute cerebrovascular disease: including acute cerebral infarction and acute cerebral hemorrhage, and S100 protein is more studied in cerebral infarction. It has an important role in the diagnosis and prognosis of acute cerebral infarction as an aid to judgment. In cerebral hemorrhage, there is relatively little research, but S100 protein is also relatively important for the differentiation of cerebral infarction and cerebral hemorrhage; 2. Cardiogenic ischemic-hypoxic brain injury: mainly in patients with cardiac arrest, S100 protein is significantly elevated. The determination of protein content can be used to determine the prognosis of patients with cardiac arrest and the degree of brain injury; 3, multiple sclerosis: it is an inflammatory disease of the nervous system, and S100 protein can be used as a biochemical marker of whether the disease is active.