Abstract： The study was designed to investigate the value of PD-1 expression on T cells in early diagnosis and prognosis of sepsis.From January 2019 to December 2022,135 patients with sepsis admitted in intensive care unit of Fengxian Central hospital were enrolled.According to the severity of sepsis,the patients were divided into sepsis group(n=89),severe sepsis group(n=22)and septic shock group(n=24).The general clinical data,laboratory indexes,constituent ratio of T cell subsets and the expression of PD-1 on the cell surface were recorded within 24 hours after the admission.Data showed that after considering sex,age and other factors,the expression of CD4+PD-1 and CD8+PD-1 were positively correlated with the severity of sepsis(P<0.05).The mortality of sepsis group,severe sepsis group and septic shock group increased successively(P=0.002).C-reactive protein(CRP),septic shock,CD4+T cells,CD4/CD8,CD4+PD-1 and CD8+PD-1 were independent risk factors for death in patients with sepsis(P<0.05).Restricted cubic spline(RCS)model was used to analyze the positive correlation of CD4+PD-1 and CD8+PD-1 with the risk of death in patients with sepsis.It can be concluded that CD4+PD-1 and CD8+PD-1 positively correlate with sepsis severity.CD4/CD8,CD4+T cells,CD8+PD-1,and CD4+PD-1 are independent risk factors for mortality in sepsis patients.