Objective To investigate the clinical significance of leukocytosis. MethodsWith the analysis of blood test,we summed up the importance of white blood cell count(WBC) and the clinical significance of leukocytosis. ResultsWBC count was of high clinical value,to which clinicians could refer.Leukocytosis is mainly seen in infection and leukemoid reaction. Conclusions The result of WBC test,to a certain extent,determines the clinical diagnosis and treatment of leukocytosis.