Abstract： Objective To evaluate the effect of molecular adsorbent recirculating system(MARS)in treatment of severe pneumonia complicated with multiple organ dysfunction syndrome(MODS).Methods Seventy-five patients who were diagnosed as severe pneumonia complicated with MODS were randomly divided into MARS group,continuous renal replacement therapy(CRRT)group and routine comprehensive therapy group.Flow dynamics,respiration function,liver function and renal function,coagulation function,inflammatory mediators,and Marshall scores were measured and compared before and after the treatment. The survival curves in 60 days were also compared among three groups.Results With MARS therapy,mean heart rates,peak inspiratory airway pressure,serum TBil,plasma D-dimmer levels and Marshall score were decreased;mean artery pressure,PaO2,oxygenation index,urine output,and platelet counts were increased;the levels of proinflammatory(NO,IL-6,IL-8,TNF-α and LBP)and anti-inflammatory(IL-10 and IL-13)mediator were decreased remarkably.The differences of these indicators between MARS group and other two groups were statistically significant(P＜0.05).And after MARS therapy,respiratory rate and Cr level were decreased,while SaO2 and WBC were increased significantly(P＜0.05).The 60 day-survival rate in MARS group was 80%(20/25),36%(9/25)in routine comprehensive therapy,and 52%(13/ 25)in CRRT group(P＜0.05).Conclusion MARS therapy has better effect on severe pneumonia conplicated with MODS than routine comprehensive therapy and CRRT.