Abstract： Objective To study the effect of c-myc small interference RNA(siRNA) on c-mye protein in leukemic cells, and investigate a new method of gene therapy on leukemia. Methods siRNA against c-myc mRNA were designed and synthesized. The siRNA at 100 nmol/ml density was transfected into HL-60 cells. The cells cultured at 24 h, 48 h or 72 h were collected after being transfected, and the total protein of the cells was extracted according to the instruction booklet of TRIzol reagent. The expression level of c-myc protein was examined by Western blotting. Results After being treated with siRNA of c-myc, the quantity of c-myc protein was obviously reduced. It was remarkably lower than that of the control group. Furthermore after 72 h treatment with siRNA, the expression of c-myc protein reached its lowest. Conclusion The siRNA of c-myc can suppress the expression of c-myc protein in HL-60 cells. There are sequence targeted and time-dependence effect. The siRNA of c-myc may become a new tool of gene therapy on leukemia.