Objective To evaluate the effect of extracorporeal membrane oxygenation(ECMO) for critical acute respiratory distress syndrome(ARDS).Methods Twenty-two patients with critical ARDS were treated with ECMO after failure of conventional ventilation therapy.The PaO_2,PaCO_2,DO_2,VO_2 and hemodynamic parameters were retrospectively analysed.Result PaO_2,DO_2,VO_2 was improved significantly after ECMO.Sixteen patients survived.Conclusion Whenever other treatments fail to improve PaO_2 on critical ARDS patients,ECMO should be considered.