Aims: This study aimed to assess the relationship between CCI and 90-day mortality among AKI patients with CRRT. Methods: CCI is a scoring system predicting short- and long-term mortality risk. A secondary analysis of the Dyrad database from 2009 to 2016 was carried out. Demographic and clinical data were collected at baseline, while mortality was calculated 90 days after CRRT. Statistical analyses were performed using R and SPSS. This study enrolled 826 patients including 496 (60%) males and 330 (40%) females with an overall median age of 63.42 years. They were divided into low-, medium-low-, medium- and high-risk groups according to different CCI scores (0, 1-2, 3-4, >4) at baseline. Results: Univariate and multivariate analyses both showed positive correlation between CCI and mortality risk (p<0.05). Kaplan-Meier analysis showed increased mortality over groups with increased levels of mortality risk. For each point increase in CCI, the 90-day mortality risk would increase by 13.3% if CCI is less than 4.037 (p<0.001) and increase by 1.3% if CCI went beyond 4.037 (p=0.7855). Conclusions: CCI is significantly associated with 90-day mortality in AKI patients with CRRT. Further studies may focus on more recent data from various data repositories and compare CCI against other scoring systems to ensure its validity in predicting prognosis among AKI patients with CRRT in clinic.