In vitro cytotoxicity test not only confirmed that affi-F/AuNPs had selective inhibition effect on cancer cells with different HER2 expression levels, but also proved that Dox@affi-F/AuNPs produced a higher synergistic killing activity than the simple mixture of Dox and FUdR on HER2 overexpressing breast cancer cells. This evidence concerns the gene ERBB2 and breast carcinoma.