In 1951, Dameshek first proposed that chronic myelogenous leukemia (CML), polycythemia vera, essential thrombocythemia, and idiopathic myeloid metaplasia (agnogenic myeloid metaplasia, AMM) are all related to myeloproliferative syndrome. Although each disease has unique clinical, laboratory, and biological characteristics, the common feature is the polyclonal proliferation involving all myeloid cells, indicating that the disease occurs in multipotent hematopoietic stem cells. Chronic leukemia is rare in children, accounting for about 3% to 5% of childhood leukemia. The clinical manifestations of CML in infancy are significantly different from those of adult CML, so pediatric CML is generally divided into juvenile and adult types. The onset age of adult chronic myeloid leukemia in children is over 5 years old, more common in 10 to 14 years old, and rarely seen in children under 3 years old, with little difference between boys and girls.