Children with fever white blood cells 20 × 10⁹ / L, is not necessarily leukemia, may be rheumatic immune diseases, bacterial infections, etc., can also appear fever and high white blood cells. The normal range of leukocytes in children is related to age, and the normal value of leukocytes in children is (5-12) × 10⁹/L. If fever and elevated leukocytes are present, clinically, they are often caused by infections, such as bacterial infections, e.g. pneumonia, nephritis, etc.. It may also be a rheumatologic immune disease, such as juvenile idiopathic arthritis. Leukemia occurs due to the emergence of a large number of clonal leukemia cells, inhibiting normal hematopoiesis, blood tests can be found in the red blood cells, white blood cells, platelets, three systems of reduction, early symptoms of high fever, anemia, bleeding and other manifestations, pathological examination can be clearly diagnosed. In conclusion, the child bleeding and fever with high white blood cells is not necessarily leukemia; if you suspect the occurrence of leukemia, it is recommended to improve the blood test to make a clear diagnosis.