Abstract: Objective To summarize the clinical experience of plasma exchange （PE） during recardiopulmonary bypass (CPB) of patients with severe haemolysis in cardiac surgery. Methods Between January 2001 and December 2005, five patients required PE for severe haemolysis after cardiac surgery. There were periprosthetic leakage and infective endocarditis in 3 patients, congenital heart disease of pulmonary artery stenosis with unsatisfied right ventricular outflow tract patching in 1 patient and thrombosis during extracorporeal membrane oxygenation (ECMO) in 1 patient. They all need blood purification to avoid acute renal failure. Results Five patients were successfully treated with PE during CPB without major complications. The amount of plasma and blood transfused in the 5 patients were 2.2±0.8L and 0.6±0.3L respectively. The volume of plasma exchange and ultrafiltrate were 3.9±1.8L and 2.4±1.3L respectively.The electrolytes and bloodgas analysis in all patients were maintained at the normal levels. The hemodynamics was stable. After heart resuscitation CPB stopped smoothly. Disappearance of periprosthetic leakage and satisfaction of right ventricular outflow tract patching were observed by echocardiograms after peration.Extubation was performed 24h after the operation in 5 patients, and they were discharged 12 to 53 d after the operation with fully recovery. The urine was clear and the body temperature was normal. Before they left thehospital, the concentration of free hemoglobin was tested in 3 patients. The concentration of free hemoglobin was slightly higher in 1 patient (68mg/L), and normal in 2 patients (lt;40mg/L). Conclusion PE during CPB in severe haemolysis is a safe technique which can effectively prevent acute renal failure caused by severe mechanical haemolysis after cardiac surgery.