Purpose To investigate the effect and mechanism of norcantharidin(NCTD)on invasion of human breast cancer cell line MCF-7 in vitro.Methods MTT assay Was used to determine MCF-7 cell proliferation,Transwell kit was used to determine cell migration,treated with NCTD on 200,400,600 μmol/L,to detect the expression of CXCR4 and CXCL12 in the control and treatment groups by real time PCR and Western blot.Results NCTD had inhibitive effects on proliferation and invasion of human breast cancer cell line MCF-7 in a dose-dependent manner,with the IC_(50) value of 582 μmol/L at 24 h,and the expression of CXCR4 Was deCreased in NCTD groups in vitro.Conclusion NCTD in vitro inhibits invasion and metastasis of human beast cancer cell line MCF-7 throush the down regulation to the expression of CXCR4.