The invention belongs to the field of traditional Chinese medicine pharmacy, and relates to the novel medical usage of icaritin, in particular to the usage of icaritin in preparation of medicine for preventing and treating endotoxemia. Lipopolysaccharide (LPS) is used for stimulating the macrophage system RAW264.7 of a mouse and establishing an extraneous endotoxic inflammation model, LPS is used for stimulating the C57BL / 6J mouse and establishing the endotoxemia animal model, icaritin is adopted for intervention, and dexamethasone is used as reference. The experiment result shows that the icaritin can reduce the death rate, the level of the inflammatory factor, the inflammatory mediator and the adhesion molecules and infiltration of inflammatory cells of the tissue after the mouse is attacked by endotoxin, and proves that the icaritin can effectively prevent and treat endotoxemia and can be used for further preparing effective drug for preventing and treating endotoxemia, including dosage forms such as oral and enteric capsules or intravenous injections.