In this study, we firstly found UCA1 expression level was correlated with ER+ breast cancer progress and migration, then we found knockdown of UCA1 could enhance chemosensitivity of breast cancer cell to tamoxifen, therefore these convincing evidences indicate a close correlation between the lncRNA UCA1 and the breast cancer drug resistance to tamoxifen. This evidence concerns the gene ESR1 and breast carcinoma.