Objectives: CRRT is frequently needed in patients with acute kidney injury (AKI) after open aortic surgery. However, the benefits on early versus standard initiation of CRRT in these patients are unclear. This study aimed to study the effect of early initiation of CRRT in patients underwent aortic surgery Methods: Data were retrieved from the Severance Open Big Data Portal (2005-2021). A total of 146 patients treated with CRRT after open aortic surgery due to aortic dissection or aneurysm were analyzed. The patients were divided into early or late CRRT group based on the median 6-hour urine output before CRRT initiation. Propensity score matching (PSM) analysis was performed to compare 7- and 28-days mortality in each group (N=136). Results: The mean age of patients were 74.5 ± 15.1 years and 100 (65.4%) were men. During a median follow-up of 27.0 [13.8 – 49.0] days, 52 and 80 cases of deaths were occurred in 7- and 28-days. The mean amount of 6-hour urine output before CRRT initiation were 498.1 ± 360.4 mL and 79.1 ± 65.8 mL in early and standard groups (P<0.001). When the mortality risks were compared with Cox regression analysis after PSM, no benefits were found in early group compared to standard group (Hazard ratio [HR], 1.32; 95% confidence interval [CI], 0.76-2.31; P=0.33 for 7-days mortality; HR, 1.44; 95% CI, 0.91-2.28; P=0.11 for 28-days mortality). When durations of CRRT, ICU stay and total hospitalization after CRRT initiation were compared, no benefits were found in early group. However, in survivors, early group were less frequently commenced to maintenance hemodialysis than standard group (odds ratio, 0.33; 95% CI, 0.11-0.99; P=0.04) Conclusions: Early initiation of CRRT in patients undergoing aortic surgery has no benefit on survival rate. However, it may reduce the frequency of commencement to hemodialysis