FLT3, a member of the class III receptor tyrosine kinases (RTKs), is preferentially expressed on the cell surface of hematopoietic progenitors, and the ligand of FLT3 (FL) is expressed as a membrane-bound or soluble form by bone marrow stroma cells. It has been disclosed that FL-FLT3 interaction plays an important role in the maintenance, proliferation and differentiation of hematopoiesis. FLT3 is also expressed in a high proportion of acute myeloid leukemia (AML) and B-lineage acute lymphoblastic leukemia cells. Activating mutations of FLT3 are the most frequent genetic lesions in AML, and AML patients with FLT3 mutations have a worse prognosis than those with normal FLT3. Exploring the mechanism by which FLT3 mutations cause autoactivation and uncontrolled signaling might lead to a better understanding of how FLT3 becomes oncogenic and provide insights for the development of new drugs.