Abstract: The present invention provides use of a multi-target protein kinase inhibitor compound A or a pharmaceutically acceptable salt thereof in the manufacture of a medicament for treating leukemia, and provides a method for treating acute myeloid leukemia, especially acute myeloid leukemia with FLT3 mutation, with compound A. In clinical trials, compound A has certain efficacies both on acute myeloid leukemia with FLT3-ITD mutation and/or FLT3-TKD mutation, and on DEK-CAN positive acute myeloid leukemia with FLT3-ITD mutation. Patients with relapsed and/or refractory acute myeloid leukemia who have failed treatment previously with Type II FLT3 inhibitors (e.g., sorafenib) can still clinically benefit from the treatment with compound A.