Objective To investigate the clinical characteristics of sepsis-associated acute kidney injury (SI-AKI) patients in intensive care unit (ICU) and the impact of timing of continuous renal replacement therapy (CRRT) on 28-day prognosis in them. Methods A retrospective analysis was made on 44 SI-AKI patients hospitalized in Department of Critical Care Medicine, the First Medical Center of Chinese PLA General Hospital from June 2017 to December 2018. According to whether CRRT was performed within 48 h after the occurrence of AKI, 29 patients were assigned into the early CRRT group, and the other 15 patients into the late CRRT group. Their physiological indicators and 28-day outcomes were compared between the 2 groups. SPSS statistics 17.0 was used to perform the statistical analysis. Kaplan-Meier survival analysis was employed to analyze the 28-day prognosis of the patients. Results According to the Kidney Disease:Improving Global Outcomes (KDIGO) Clinical Practice Guideline, there were 6(13.6%) patients at AKI stage 1,8(18.2%) at stage 2, and 30(68.2%) at stage 3. The patients having transient AKI accounted for 18.2%(8/44), and persistent AKI for 81.8%(36/44). Within 28 d after AKI occurrence, 15 cases died. The early CRRT group had a higher proportion of diabetes mellitus (31.0% vs 6.7%, P=0.048), and obviously lower levels of systolic blood pressure [(114±15) vs (130±15)mmHg,P=0.005] during the process of CRRT, mean arterial pressure [(82±11) vs (91±18)mmHg, P=0.040], serum creatinine (197.0 vs 418.9μmol/L, P=0.002,), urea nitrogen (12.9 vs 35.0mmol/L, P<0.001), serum calcium (1.9 vs 2.0mmol/L, P=0.007), serum magnesium (0.7 vs 0.8mmol/L, P=0.013), elevated serum levels of hemoglobin [(96±26) vs(84±13)g/L, P=0.041] and lactic acid (3.8 vs 1.7mmol/L, P=0.009), and lower proportion of those at AKI stage 3 (58.6% vs 86.7%, P=0.041), when compared with the late CRRT group. The 28-day mortality was 31% (9/29) in the early CRRT group, and 40%(6/15) in late CRRT group, and there was no significant difference between the 2 groups (P=0.575). Conclusion Early CRRT does not improve 28-day mortality in SI-AKI patients.