Objective To evaluate the role of new neutrophil parameters(NEU-X,NEU-Y and NEU-Z)in the auxiliary diagnosis of sepsis.Methods Totally,55 sepsis inpatients,73 non-sepsis inpatients and 175 healthy subjects from the North Branch of Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from January to December 2021 were enrolled.C-reactive protein(CRP),white blood cell(WBC)count,the absolute value of neutrophils(NEUT#)NEUT count and NEU-X,NEU-Y and NEU-Z were compared among the 3 groups.The correlation between NEU-X,NEU-Y,NEU-Z and procalcitonin(PCT)in sepsis group was analyzed by Pearson analysis.Sepsis group was sub-classified into Gram-negat=ive bacterium infection group,Gram-positive bacterium infection group and fungal infection group,and the differences of NEU-X,NEU-Y and NEU-Z among the 3 groups were compared.Receiver operating characteristic(ROC)curve was used to evaluate the efficacy of NEU-X,NEU-Y and NEU-Z in diagnosing sepsis.Results NEU-X and NEU-Y in sepsis group were higher than those in healthy control group and non-sepsis group(P<0.001),CRP,WBC count and NEUT#were higher than those in healthy control group(P<0.001),but there was no statistical significance between them and non-sepsis group(P>0.05).NEU-X,NEU-Y and NEU-Z were positively correlated with PCT(r values were 0.392 5,0.532 3,0.416 0,P<0.01).NEU-Y in fungal infection group was lower than that in Gram-negative bacteria infection group(P<0.05).The area under curve of NEU-Y for the diagnosis of sepsis was 0.681 8[95%confidence interval(CI)0.588 9-0.778 4].The area under curve of NEU-Y was 0.810 3(95%CI 0.731 0-0.889 7).Conclusions NEU-X and NEU-Y can be used in the auxiliary diagnosis of sepsis.