Abstract: OBJECTIVE To compare the effects of renal replacement therapy at different times on the prognosis of patients with kidney injury（AKI） caused by sepsis in the intensive care unit（ICU）. METHODS Total of 120 patients with kidney injury caused by sepsis, who were admitted to ICU of the hospital between Jul. 2017 and Dec. 2019 were retrospectively analyzed. According to the time of receiving continuous renal replacement therapy（CRRT）, the subjects were divided into the early group（n=57, AKI≤grade 2 at the beginning of CRRT） and late group（n=63, AKI of grade 3 at the beginning of CRRT）. The general data, main outcome indexes after treatment, 28-day survival rate, total mortality and incidence of complications were compared between the two groups. RESULTS Before the treatment, the Sequential Organ Failure Assessment（SOFA） scores, white blood cell count（WBC） in the early group were significantly lower than that in the late group（P＜0.05）. The duration of CRRT and length of ICU stay in the early group （12.41±1.48）d,（11.41±1.24）d were significantly shorter than that in the late group （16.14±1.65）d,（13.57±1.42）d. After the treatment, the oxygenation index and the recovery rate of renal function in the early group （206.41±21.48）, 91.23% were significantly higher than that in the late group （156.71±16.23）, 77.78%（P＜0.05）. The 28-day mortality rate and incidence of acidosis in the early group（33.33%, 1.75%） were significantly lower than that in the late group（52.38%, 14.29%）（P＜0.05）. CONCLUSION The prognosis of patients with AKI caused by sepsis in ICU is poor. The timing of CRRT should be chosen in patients before their renal function progressing to AKI stage 3. Early treatment can improve the patient's short-term prognosis, reduce the 28-day mortality, promote renal function recovery, and reduce CRRT related complications.