Clinic test reveal that by contrasting with expression in E.coli the human granulocyte-macroghage colony-stimulating factor( hGM-CSF) which expression in Pichia Pastoris has lower toxity and side-effect rate. Due to nonglycosylated hGM-CSF has higher biological activity in vivo, we mutant glycosylated positions by using PCR technique. The mutant GM-CSF gene was inserted into PPIC9K and then transformed into Pichia Pastoris strain GS115 for high expression. The results demonstrat that, in spite of the mutation, the expression product also has natural biological activity.