Abstract: Objective　To establish the reference intervals of the white blood cell volume，nucleus-cytoplasm ratio and the granules of plasma in healthy subjects，and to evaluate the clinical application in screening sepsis and leukemia. Methods　Peripheral blood samples from 290 healthy subjects（including 137 males and 153 females），42 infective patients（including 23 males and 19 females） with positive blood culture（excluding any hematological disease）and 260 patients（including 147 males and 113 females） with various leukemia were collected. Then，the reference intervals of the white blood cell VCS parameters were established and analyzed statistically. The cut-off values with high sensitivity and specificity were chosen by receiver operating characteristic（ROC） curves in screening sepsis and leukemia. Results　The reference intervals of VCS parameters were obtained by the data analysis. Mean channel of lymphocyte conductivity（MLC） was a useful indicator in discriminating the healthy subjects and patients with sepsis and leukemia. The parameters of mean channel of neutrophil conductivity（MNC） could be used as indicators in distinguishing sepsis from leukemia. Myeloid leukemia and lymphocytic leukemia could be discriminated by mean channel of lymphocyte volume distribution width（MLV-SD）. Mean channel of nononuclear cell conductivity distribution width（MMC-SD） was a good indicator in distinguishing acute myelogenous leukemia（AML） from chronic myelogenous leukemia（CML）. mean channel of lymphocyte volume（MLV） was useful in discriminating acute lymphoblastic leukemia（ALL） and chronic lymphoblastic leukemia（CLL）. Conclusions　The establishment of reference intervals of the white blood cell VCS parameters makes it possible to deciding earlier whether there is an infection with bacteria and leukemia. VCS parameters not only reflect morphological changes of immature cells in peripheral blood samples when it comes to sepsis or leukemia，but also is used to screen leukemia quickly，economically and effectively.

Key words: Reference interval, VCS parameter, Leukemia, Bacterial infection