Acute lung injury is a common complication of subarachnoid hematoma (SAH), and a significant risk factor for death in patients with SAH. Unlike neurogenic pulmonary edema and pneumonia following brain injury, the clinical causes of pulmonary injury after SAH are not intracranial hypertension or pulmonary infection. Its occurrence is influenced by the release of catecholamines, the regulatory function of the hypothalamic-pituitary-adrenal (HPA) axis and systemic inflammatory response, but the specific mechanisms are still unclear. Therefore, delving into the pathological mechanisms of SAH-induced lung injury and developing therapeutic strategies based on the findings is of great importance to improve the prognosis of patients. Abnormal accumulation of hyaluronic acid in the lungs has been reported to be closely related to the pathological progression of various pulmonary injury diseases, such as chest trauma, pulmonary infection and chronic obstructive pulmonary disease. From this, the present research is aimed to explore the levels and dynamic changes of hyaluronic acid in the bronchoalveolar lavage fluid and blood of patients with acute lung injury following SAH, and to analyze its correlation with the prognosis of pulmonary complications, thereby providing assistance for the clinical diagnosis and treatment of SAH.