【Abstract】 Acute respiratory distress syndrome (ARDS) is a common respiratory disease with rapid progression, high mortality and complex pathogenesis. Histone is the basic unit of chromatin, which is called extracellular histone when released into extracellular space, and plays a role as an inflammatory mediator and a platelet agonist in the pathogenesis of ARDS. The current paper discussed the understanding of ARDS: the basic pathophysiological changes of ARDS, the pathological changes of the lungs and the present clinical therapy, three main sources of extracellular histones and the possible mechanism by which extracellular histones function in ARDS. We also discussed the prospect of extracellular histone as a new therapeutic target for ARDS in the future.