Objective To evaluate etiological and prognostic factors contributing to acute renal failure (ARF) after cardiac surgery. Methods A retrospective study was carried out in patients with ARF after cardiac surgery. Cox regression analysis was performed to analyse prognostic factors. Results The contributing factors to ARF were cardiac hypotension (in 50 cases), hemolysis (in 8 cases), respiratory failure (in 4 cases), severe infection (in 3 cases), interstitial nephritis (in 1 case) and uncertain factors (in 42 cases). Renal function was recovered in 47 patients (43.5%), 38 patients survived (35.2%), 70 patients died (64.8%). The causes of death were as follow multiple organ dysfunction syndrome（MODS）(33 cases), heart failure (26 cases), respiratory failure (2 cases), hyperkalemia(4 cases), hemorrhage shock (2 cases), brain damage (1 cases), DIC (1 cases) and asphyxia (1 cases). Univariate analysis showed that the mortality rates were significantly higher in patients with oliguria (OR:10.4), persistent hypotension (OR:21.4), artificial ventilation more than 3 days(OR:18.3), coma (OR:9.4) and digestive tract bleeding (OR:4.11). To 76 oliguria patients, mortality rate was higher in non-dialysis group (Odds R=4.829, 95%CI: 1.002～23.275). Forward Stepwise Cox Regression analysis showed that persistent hypotension, oliguria, the number of impaired organs and non-dialysis were the most important factors correlated with death (P＝0.010,0.00,0.034 and 0.01 respectively). Conclusion Persistent hypotension was the major cause of ARF following cardiac surgery. The majority of those patients died of MODS or heart complications. Oliguria, persistent hypotension, more impaired organs and non-dialysis were the strong prognostic factors of death. Early blood purification may ameliorate the prognosis of oliguria patients.