Abstract: Objective To explore the effects of long non-coding RNA HOX transcript antisense intergenic RNA (HOTAIR) on radiotherapy sensitivity of breast cancer cells and related mechanism. Methods The expression of HOTAIR in breast cancer tissues and cell lines was detected. SKBR3 cell line with low HOTAIR expression was adopted in the following studies. Lentivirus transfection was used to establish the cells with overexpression of HOTAIR. After radiotherapy, their proliferation, viability and invasion were detected by plate colony formation assay, CCK-8 assay and Transwell chamber assay. The effects of HOTAIR on the expression of Beclin1, LC3Ⅰ, LC3Ⅱ, mTOR and p-mTOR were detected by Western blot. Results The expression of HOTAIR in breast cancer tissues was higher than that in adjacent non-caner tissues (P<0.05). Compared with normal breast epithelial cells, lncRNA HOTAIR was highly expressed in breast cancer cell lines (P<0.05). The overexpression of HOTAIR significantly increased the proliferation, viability and invasion abilities of SKBR3 cells (P<0.05). Compared with the control group, the HOTAIR overexpression group presented increases in LC3Ⅱ/LC3Ⅰratio and Beclin1 expression as well as decreases in the expression of p-AKT and mTOR (P<0.05). After treatment with mTOR receptor inhibitor RAPA, the expression of mTOR and p-AKT was significantly inhibited in both groups, and the level of Beclin1 and LC3Ⅱ/LC3Ⅰratio significantly increased. There was no significant difference in the expression of the above proteins between the two groups (P>0.05). Conclusions HOTAIR overexpression enhances the viability and invasion ability of SKBR3 cells after radiotherapy, as well as the radiation resistance of SKBR3 cells, which may be related to enhanced autophagy in breast cancer cells through regulation of the mTOR signaling pathway.