Molecular genetics plays an irreplaceable role in the diagnosis of MICM classification of childhood leukemia.The majority of leukemia cases have one of a series of chromosome abnormalities,many of which are associated with specific morphological and clinical characteristics.Fusion gene as a structural rearrangement of the gene product are considered to be leukemia-specific molecular markers.Therefore,the detection of fusion gene can be used for diagnosis of leukemia,diagnosis of minirnal residual disease,prognosis and targeted therapy.Originally,the detection of various types of childhood leukemia in the field of molecular genetics detected by traditional methods,such as polymerase chain reaction.In the past few decades,there were various methods developed,such as multiplex reverse transcription polymerase chain reaction,real-time quantitative reverse transcriptase polymerase chain reaction,fluorescence in situ hybridization,comparative genomic hybridization,flow cytometry technology,whole-genome sequencing.