Objective:To study the inhibitory effects of Changweiqing on chemotherapy induced lung metastasis of colon cancer in mice and explore its mechanism. MethodsThe chemotherapy induced lung metastasis of colon cancer model was established by one-time intraperitoneal injection of oxaliplatin(L-OHP)at maximum tolerable dose and intravenous injection of colon cancer CT26 cells via caudal vein 3 days later. 24 BALB/c mice were randomly divided into the model group,chemotherapy induced lung metastasis(L-OHP)group,Changweiqing plus chemotherapy induced lung metastasis(CWQ+L-OHP)group. The nodules number of lung metastasis was counted,the tumor lesions in the lung were detected by HE staining,the microvessel density(MVD)of lung metastatic tumor tissue was detected by immunohistochemistry,and the protein and mRNA expressions of vascular endothelial growth factor(VEGF)-A,matrix metalloproteinase 2/9(MMP2/9)in the lung metastasis were detected by Western blot and qRT-PCR.  Results:Compared with the L-OHP group,the nodules number of lung metastasis was reduced in the CWQ+L-OHP group(P<0.05),and the MVD value of tumor tissue was decreased(P<0.01),and the protein and mRNA expressions of VEGF-A,MMP2 and MMP9 in the lung tissue were all down-regulated(P<0.01).  Conclusion:Changweiqing can inhibit chemotherapy induced lung metastasis of colon cancer in mice. Its mechanism may be related to down-regulating the expressions of VEGF-A,MMP2 and MMP9 in tumor tissue and reducing MVD and tumor angiogenesis.