Objective To investigate the effect and mechanism of up-frameshift 1 (UPF1) on invasion, migration and epithelial mesenchymal transition (EMT) of human breast cancer cell AU565. Methods The fresh cancer tissues and normal breast tissues of 43 breast cancer patients who underwent mastectomy in the hospital from September 2021 to March 2022 were collected, paraffin blocks were prepared, and the expression of UPF1 was detected by immunohistochemistry. Human breast cancer cell line AU565 and human breast epithelial cell line DU4475 were purchased, and the UPF1 level was measured by laser confocal scanning microscope. The recombinant cells with low expression of UPF1 were constructed by small interfering RNA (siRNA) technology, and the effects of transfection of siRNA-UPF1 on the invasion and migration ability of AU565 cells, EMT-related protein expression and protein kinase B/ mammalian target of rapamycin (Akt/mTOR) signal pathway were analyzed. Results The absorbance of UPF1 in breast cancer tissue was significantly higher than that in normal breast tissue (P<0.05). The fluorescence intensity of UPF1 in AU565 cells was significantly higher than that in DU4475 cells (P<0.05). Compared with the siRNA-NC group, the expression levels of UPF1 protein and mRNA in AU565 cells were significantly decreased after transfection of siRNA-UPF1 (P<0.05). Compared with siRNA-NC group, the membrane penetration rate and cell migration rate of AU565 cells after transfection of siRNA-UPF1 were significantly increased (P<0.05). The expression levels of E-candherin and Vimentin and N-cadherin in AU565 cells decreased significantly after transfection of siRNA-UPF1 (P<0.05). The levels of p-Akt and p-mTOR in AU565 cells were significantly increased after transfection of siRNA-UPF1 (P<0.05). Conclusion UPF1 is upregulated in breast cancer, but silencing UPF1 may promote the invasion and migration of breast cancer cell AU565 and induce EMT by activating Akt/mTOR pathway