Objective: To investigate the effect of polypeptide extract from scorpion venom (PESV) on the matrix metalloproteinase2（MMP2）and matrix metalloproteinase9（MMP9）expression in leukemia-NOD/SCID mice, and the intervention mechanism of PESV in the multiplication and infiltration of leukemic cells thereof. Methods: In order to establish the animal model of outer marrow infiltration of human leukemia，bone marrow mononuclear cells of leukemia patients, irradiated 270 cGy on body by ~(137)Cs, were injected into NOD/SCID mice. The mice were randomly divided into five groups. The groups I, II and III were treated with different concentrations of PESV. Group Ⅳ was the model group injected by the normal saline solution. GroupⅤ was taken as control. The peripheral white blood cell count and blood smear were observed in groups. All of the mice were killed after four-week observation and MMP2 and MMP9 expressions were examined using Real timePCRmethod. Results: The expression levels of MMP2 and MMP9 were significantly lower in group I, group II and group III than that of the model group(P < 0.05). The expression levels of MMP2 and MMP9 were related to the concentration of PESV. Moreover, the peripheral white blood cell count and blood smear were more normal in mice treated with PESV than those of mice of model group. Conclusion: PESV inhibited the overexpression of MMP2 and MMP9 in leukemia-NOD/SCID mice, which significantly inhibited the multiplication and infiltration of leukemic cells.