〔Abstract〕 To investigate the expression of HSPA8 in breast cancer and its effect on tumor biological behaviors . Methods Bioinformatics analysis and immunohistochemistry assays were used to detect the expression of HSPA8 in breast cancer and adjacent non-tumor breast tissues , and the relationship between its expression and clinicopathological characteristics of breast cancer patients was analyzed . Correlation between HSPA8 expression and prognosis of breast cancer patients was analyzed by Kaplan-Meier Plotter database . HSPA8 knockdown and overexpression breast cancer stabilized cells were constructed , respectively. CCK-8 , clone formation , Transwell , cell scratch , Western blot and immunofluorescence assay were used to detect the effects of HSPA8 on the prolifera- tion , invasion and migration of breast cancer cells , and its effect on epithelial-mesenchymal transition (EMT) . Results Bioinformatics analysis and immunohistochemistry assay revealed that the expression of HSPA8 in breast cancer tissues was higher than that in adjacent non-tumour tissues (P < 0. 05) , and its expression level of the pro- tein was significantly and positively correlated with the tumor size , histological grade , lymph node metastasis and Ki-67 proliferation index (P < 0. 05) . The Kaplan-Meier survival curve showed that high expression of HSPA8 was significantly associated with poor prognosis in breast cancer patients (P < 0. 05) . CCK-8 , clone formation , tran- swell , cell scratch , Western blot and immunofluorescence assay showed that knockdown of HSPA8 expression could significantly inhibit the proliferation , invasion , migration function and EMT of breast cancer cells ( P < 0. 05 ) , while overexpression of HSPA8 could significantly promote the proliferation , invasion , migration function and EMT of breast cancer cells ( P < 0. 05) . Conclusion HSPA8 is highly expressed in breast cancer tissues , which is closely related to disease progression and the malignant phenotype of breast cancer , suggesting that HSPA8 may be a potential biological target for breast cancer treatment.