ObjectiveTo investigate the changes in CD8+ T lymphocyte count and effect on immune function in patients with sepsis after continuous renal replacement therapy (CRRT).MethodsGeneral data of septic patients who admitted to the emergency department of a hospital between October 2015 and August 2016 were collected, peripheral blood was taken from patients before and after single CRRT, the total CD8+T cell count, interferonγ（IFNγ）secreting CD8+ T cell count, the levels of inhibitory molecules and costimulatory molecules as well as IFNγ and tumor necrosis factorα（TNFα）produced by CD8+ T cells were detected.ResultsA total of 37 hospitalized septic patients were infected with gramnegative bacteria, pathogens causing infection were Klebsiella pneumoniae (22 strains), Acinetobacter baumannii (11 strains), and Enterobacter cloacae (3 strains). After CRRT, the body temperature, heart rate, white blood cell count, urea nitrogen, and serum creatinine levels in septic patients were all lower than those before CRRT (all P<0.05). After CRRT, the total CD8+ T cell count in septic patients didn’t change significantly (P>0.05), but IFNγsecreting CD8+ T cell count increased (P<0.05). Levels of cytotoxic T lymphocyteassociated antigen 4(CTLA4）, programmed death1 (PD1), Tcell immunoglobulin and mucindomaincontaining molecule 3 (TIM3) after CRRT were all lower than those before CRRT (all P<0.05), while levels of costimulatory molecules CD28 and secreting IFNγ elevated after CRRT(all P<0.05).ConclusionCRRT can not only improve the vital signs and renal function of patients with sepsis, but also enhance the immune function of CD8+ T cells.