Objective To find out the factors affecting the outcome of severe acute respiratory distress syndrome (ARDS) patients treated with extracorporeal membrane oxygenation (ECMO).Methods From November 2008 to September 2010,patients with severe acute respiratory distress syndrome (ARDS) required extracorporeal membrane oxygenation (ECMO) after failure of conventional therapy were retrospectively studied.Patients treated by veno-arterial ECMO,treated by mechanical ventilation for more than l0 days were excluded.All patients were divided into survival group and non-survival group,according to the 28 day survival situation after ECMO treatment.We compared the clinical data of the two groups when transferred to Intensive Care Unit (ICU),before and after ECMO treatment.We used Independent-samples t test and Chi-square tests to find out the factors affecting the results of ECMO treatment in the patients with severe ARDS.Results A total of twenty-five patients were enrolled in the study,of whom 15 patients survived,10 patients died.The results showed that the average age of the survival group is lower than that of non-survival group (49.8 ± 10.5) vs.(59.9 ± 11.5),P =0.044,and the proportion of patients with severe ARDS caused by Influenza A (H1 N1) in the survival group was higher than that of the non-survival group (x2 =4.453,P =0.048).In addition,the duration of mechanical ventilation before ECMO treatment in the survival group was shorter than that in the non-survival group (57.8 ± 8.7) hours vs.(68.3 ±13.7) hours,P =0.013.Conclusions The age,pre-ECMO ventilation duration and the cause of ARDS are the important factors influencing the efficacy of ECMO treatment in the patients with severe ARDS.