Objective To evaluate the efficiency and prognosis of continuous renal replacement therapy(CRRT) in patients with multiple organ dysfunction syndrome(MODS) and acute renal failure(ARF) after cardiac surgery. Methods Fourty-seven patients with MODS and acute renal failure(ARF) after cardiac surgery were treated with CRRT. They were divided into two groups according to prognosis:26 survival as group A and 21 death as group B.MODS scores,APACHE Ⅲ scores,heartfunction grade before surgery, duration of extracorporeal circulation,duration from ARF and urine volume ＜0.5ml·Kg-1·h-1 to CRRT, mean arterial pressure（MAP）, oxygenic index,blood urea nitrogen（BUN） and serum creatinine（Scr）were analyzed and compared. Results ① Before CRRT the numbers of impaired organs of patients in group B were significantly more than that in group A（P<0.05）; ② MODS scores （12.5±2.8 vs 7.6 ± 2.7，P<0.05） and APACHE Ⅲ scores （85.1±16.8 vs 71.1±16.7，P<0.05）of group B were significantly higher than that of group A before CRRT. After a 12-hour,s treatment of CRRT, APACHE Ⅲ scores and MODS scores in group A were significantly decreased (P<0.05); ③ After a 12-hour,s treatment of CRRT,BUN and Scr were significantly decreased in all patients,but oxygenic index was significantly increased only in group A (P<0.05); ④ The duration of ARF before CRRT（32.3±39.3 hours vs 12.7±10.7 hours, P<0.05） and the time of urine volume ＜ 0.5ml·Kg-1·h-1 before CRRT（37.7±39.2 hours vs 15.7±14.8 hours, P<0.05）were significantly higher than that of group A. Conclusion There is higher mortality rate in patients with more impaired organs after cardiac operation.MODS scores and APACHE Ⅲ scores can be used to evaluate the severity and prognosis of patients with MODS and ARF after cardiac surgery. CRRT is an important treatment to these patients.But the most important problem in this process is the recognition of ARF and early beginning of the therapy. The prognosis of these patients correlated with early CRRT therapy.It is suggested that early CRRT therapy is beneficial for prognosis and reducing mortality rate of these patients.