Abstract: GM-CSF is the early discovered hematopoietic growth factor. Various kind of cells can synthesize and secreted GM-CSF by some stimulation. GM-CSF can stimulate the proliferation and differentiation of bone marrow hematopoietic progenitor cells and activate the proliferation and maturity of neutrophils, eosinophils, and macrophages. GM-CSF also stimulate growth of megakaryocyte and erythrocyte. Some change of GM-CSF level can be found after radiation in animal, which can accelerate the recovery of radiation injury.