Abstract: Acute respiratory distress syndrome(ARDS) is a kind of respiratory failure caused by a series of etiologies, with high mortality in critically ill patients. According to different insults, there are pulmonary ARDS and extra-pulmonary ARDS. Pulmonary ARDS damages epithelial cells and alveolar membrane directly, while extra-pulmonary ARDS damages alveolar endothelial cells and causes increased permeability, interstitial edema, and collapsed alveoli. Pulmonary and extra-pulmonary insults usually co-exist in critically ill ARDS patients so that we couldn't differentiate them according to etiology, clinical characteristics, biomarkers or mortality. In this article, the differences in risk factors, clinical features, and mortality of pulmonary ARDS and extra-pulmonary ARDS are compared, and we comb the pathogenesis, clinical manifestations, treatment and prognosis of ARDS which are extremely important. It enables intensive care physicians to have a more comprehensive understanding of the pathogenesis of ARDS, and can standardize and systematically initiate the precise assessment and treatment of ARDS, thereby reducing the mortality rate of ARDS patients.