Objective: To study the anti-tumor mechanism of Xiaoai Jiedu prescription in vivo. Method :The mice bearing tumors(estabilished by subcutaneous inoculation of H22 cells)were fed with Xiaoai Jiedu prescription.Morphology of the tissue of tumor under light microscope and tumor cells under electron microscope were observed. The matrix metall-oproteinase(MMP-2) were assayed. Result: The medium dose group of Xiaoai Jiedu prescription has the largest amount of apoptosis. There were many pinocytosises except the general morphological change in each Xiaoai Jiedu prescription group. The activity of MMP-2 had significantly decreased in the low-dose group of Xiaoai Jiedu prescription(P<0.05). Conclusion: Xiaoai Jiedu prescription has the anti-tumor effect in vivo possibly through the mechanism of inducing tumor cell apoptosis and inhibitting the activity of MMP-2.