Pediatric leukocytes are higher than adults until the age of 8. Normal adult leukocytes are (4.0 to 10.0)x10^9/L. Pediatric leukocyte count at birth is (15~20)x10^9/L, but it is not fixed, it usually rises slightly at 6~12 hours after birth and can reach (21~28)x10^9/L, then it drops to an average of 12×10^9/L at 1 week, and basically maintains at leukocyte 10×10^9/L, and after 8 years of age it can be close to the adult level. Leukocyte classification is mainly a change in the ratio of neutrophils to lymphocytes, with neutrophils higher than lymphocytes at birth, and as the number of leukocytes declines, the two ratios are essentially equal at 4-6 days, and again at 4-6 years of age, after which the leukocyte classification is similar to that of adults. Therefore, generally before the age of 8 years, newborns should have a higher white blood cell count than adults, and after the age of 8 years, they begin to approach the adult level. When pediatric leukocytes increase more than the normal range, they should consult the doctor in time to find out the cause of the disease.