Objective To investigate the efficacy of continuous renal replacement therapy (CRRT) in elderly patients with sepsis. Methods A prospective study was carried out on 156 elderly sepsis patients admitted in our hospital from January 2014 to June 2017. They were randomly divided into CRRT group and control group, with 78 cases in each group. The control group was treated with conventional therapy, and CRRT group was treated with CRRT on the basis of conventional treatment. Peripheral blood immune indices, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), procalcitonin (PCT), and high sensitivity C-reactive protein (hs-CRP) before treatment and 3 and 7 days after treatment were measured and recorded. The curative effects after 28 days’ treatment and scores of acute physiology and chronic health evaluation Ⅱ(APACHE Ⅱ), multiple organ dysfunction syndrome (MODS) and sequential organ failure assessment (SOFA) were analyzed and compared between the 2 groups. SPSS statistics 19.0 was used to analyze the data. For different data types, Student’[KG-*3]s t test, repeated measures analysis of variances or Chi-square test was employed for the com-parison between two groups. Results In the 2 groups, the peripheral blood proportions of CD3⁺, CD4⁺ and CD14⁺ in the 7th day aftertreatment were significantly higher than those before treatment and in the 3rd day, and the proportions of CD3⁺ [(69.3±8.7)% vs (63.8±8.4)%], CD4⁺ [(36.8±13.3)% vs (31.5±10.6)%] and CD14⁺[(55.7±6.8)% vs (46.8±6.5)%] in the 7th day were obviously higher in the CRRT group than the control group (P<0.05). The serum levels of IL-6, TNF-α, PCT and hs-CRP were remarkably decreased in both groups in 7 days after treatment when compared with the levels before treatment and after 3 days’ treatment (P<0.05). Their levels in the CRRT group were notably lower than those in the control group in 3 and 7 days’ after treatment [IL-6:(40.7±3.8) vs (68.4±5.2) ng/L, (18.5±2.6) vs (37.8±3.5) ng/L; TNF-α:(28.4±10.7) vs (36.5±14.2) μg/L, (20.3±7.8) vs (27.9±11.4) μg/L; PCT:(4.3±1.7) vs (6.2±2.3) μg/L, (1.3±0.8) vs (3.6±1.4) μg/L, hs-CRP:(52.6±15.4) vs (71.3±18.4) mg/L, (22.5±9.3) vs (36.4±12.7) mg/L, all P<0.05]. The scores of APACHE Ⅱ, MODS and SOFA at the 7th day were significantly lower in the 2 groups than those before treatment (P<0.05). The CRRT group had obviously lower APACHE Ⅱ score [(10.8±4.2) vs (14.3±4.8)], MODS score [(4.5±1.9) vs (6.1±2.3)] and SOFA score [(3.6±1.4) vs (5.8±1.7)] in the 7th day when compared with the control group (P<0.05). After 28 days’ treatment, the curative rate was remarkably higher in the CRRT group than in the control group (70.5% vs 48.7%, P=0.006). Conclusion CRRT, in combination with conventional treatment, improves the clinical efficacy, promotes the immune function and reduces the inflammatory responses in elderly patients with sepsis.