Objective To investigate the primary diseases, risk factors, therapy, prognosis and factors affecting prognosis of severe acute respiratory distress syndrome(ARDS). Methods Data of 34 patients with severe ARDS from January 2009 to January 2012 were retrospectively analyzed, including age, gender, history of chronic diseases, predisposing factors, vital signs within 24 h after diagnosis, laboratory tests (blood gas analysis, routine blood tests, renal function, electrolytes, procalcitonin, C-reactive protein, erythrocyte sedimentation, lactic acid, oxygenation index), acute physiology and chronic health evaluationⅡ(APACHEⅡ) score, therapeutic methods, occurrence of multiple organ dysfunction (MODS) and mortality within 21d after final diagnosis. Above indicators were compared between survival and death groups and their correlation with APACHEⅡscore was analyzed. Results Of the 34 patients with severe ARDS, there were 28 males and 6 females, ranging from 18 to 98 years [(54.09±18.34)years], including 24 death cases(70.6%). The statistics showed that APACHEⅡ score, lactic acid, procalcitonin in death group were higher than those in survival group[(23.42±4.59) vs (16.70±1.57), (4.83±3.60) vs (2.88±0.85)mmol/L, (3.02±2.87) vs (1.20±0.73)ng/L; P＜0.05], oxygenation index in death group was lower than that in survival group[(80.92±29.29) vs (112.30±24.49); P＜0.05]. APACHEⅡ score was positively correlated with blood lactic acid and procalcitonin (r=0.531, r = 0.527; P＜0.01). Conclusions Concentrations of blood lactic acid and procalcitonin were positively correlated with the severity of ARDS. The integrated therapy including treatment of primary diseases and protection of multiple organs can improve the prognosis of patients with ARDS.