Abstract: Objective To study the Anti-angiogenesis of the 5-lipoxygenase activating protein(FLAP) inhibitor,MK886, on human colonic cancer in vivo and further explore its anti-tumor mechanism. Methods HT-29 human colonic cancer cells were subcutaneously injected into the flanks of 15 nude mice to establish xenograft models. Fifteen mice were divided into three groups randomly. The mice in MK886-treated group were administered with MK886 dissolved into DMSO，and the mice in two control groups were treated with DMSO or nothing, respectively. After the treatment for one month, all nude mice were killed,and all tumors were removed.The microvessel density (MVD) of tumors was measured by using immunohistochemistry and the results were compared. Results None of the 15 nude mice died during the experiment and all nude mice formed in situ mass of colonic tumor. Immunohistochemistry, revealed that there was no significaut difference in MVD between two control groups, and the MVD in MK886-treated group was significantly decreased as compared with the no conspicuous difference was demonstrated at the MVD of tumor tissue of two control groups（P>0.05）. But the MVD of treated group was much less than control groups (P<0.05). Conclusion 5-LOX inhibitor, MK886 inhibits the growth of colonic tumor by suppressing the angiogenesis of tumor.