Objective To investigate the efficacy of continuous blood purification ( CBP) in the treatment of severe sepsis, and explore the related immune regulatory mechanisms. Methods Forty-eight patients with severe sepsis were randomly divided into a control group ( n =23) and a CBP group ( n =25) .CD4 + CD25 + regulatory T cells ( Treg% ) in peripheral blood and APACHEⅡ score were measured dynamically before treatment and 12, 24, 36, 48, 60, 72 hours after treatment. Meanwhile the length of ICUstay, duration of mechanical ventilation, and 28 day mortality were determined. Results Compared with the control group, the length of ICU stay, ventilator time, incidence of multiple organ failure, and mortality decreased significantly in the CBP group ( P lt; 0. 05) . And CBP also decreased Treg% and APACHEⅡ score significantly. There was a positive correlation between Treg% and APACHEⅡ score ( r =0. 804, P lt;0. 01) .Conclusion Early CBP treatment can reduce Treg%, improve cellular immunity and improve the prognosis of sepsis.