The high level secretive expression of hGM-CSF in streptomyces was obtained.The factors, which can influence the exogenous expression in prokaryoties, such as the distance between SD and ATG, and the features of expression induction in streptomyces,etc. were studied. Then the secreted hGMCSF protein in streptomyces using the signal peptide MEL were obtained. One third of the expression products were secreted. By the experiment of clony stimulating factor formation and cell culture of TF-1 (hGM-CSF dependent cell line)，its biological activity determined is 5 MU/L.