Abstract: Objective: To explore the effects of veno-venous hemodiafiltration on hemodynamics and oxygenation in patients with multiple organ dysfunction syndrome(MODS).Methods: In 24 patients with MODS,a double lemen catheter was put into the femoral vein,and the VVHDF was performed with the Hospal BSM22 SC.Hemodynamics,blood gas and oxygenation were measured or calculated at scheduled intervals by use of Swan-Ganz catheters.Results: The heart rate,right atrium pressure,mean pulmonary arterial pressure,pulmonary arterial wedge pressure,index of pulmonary vascular resistence decreased significantly(P<0.001 respectively) compared with those before VVHDF;the mean arterial pressure,index of systemic vascular resistence,partial pressure of arterial blood oxygen,arterial blood oxygen saturation,arterial blood oxygen content,oxygen delivery and oxygen consumption increased significantly(P<0.01~P<0.001),and the cardiac index,blood hemoglobin,partial pressure of arterial blood carbon dioxide,partial oxygen pressure in mixed venous blood,venous oxygen saturation,venous oxygen content and oxygen extraction ration did not change after treatment(P>0.05).Conclusions: VVHDF can improve the condition of hemodynamics and oxygen supply.