Objective To explore microRNA-940(miR-940) expression in breast cancer tissues and cells, as well as its effect on breast cancer cell proliferation, invasion and migration capacities and the related molecular mechanism. Methods miR-940 expression in breast cancer tissues, para-carcinoma tissues from 78 patients undergoing surgical resection in our hospital from January 2016 to January 2017, and human breast cancer cell lines MCF-7, SK-BR-3, MDA-MB-231 and BT-549, as well as that in normal human breast cell line MCF-10 A, were detected using Real-time PCR. miR-940 expression in breast cancer cell line MDA-MB-231 was up-regulated through transfection with miR-940 mimics using liposome LipofectaminsTM 2000. Changes in cell proliferation capacity were detected using CCK-8 assay, while those in cell invasion and migration capacities were detected using transwell assay. The potential target gene of miR-940 was predicted by biologic information method , binding of miR-940 with the 3’UTR of CXC chemokine receptor 2 (CXCR2) was detected using dual luciferase reporter assay, and the effect of miR-940 on CXCR2 protein expression was detected using Western blotting. Results miR-940 expression in breast cancer tissues and cells was remarkably down-regulated (P<0.01), and miR-940 expression was closely correlated with TNM stage and lymph node metastasis (P<0.01). Up-regulating miR-940 expression in MDA-MB-231 cells would lead to markedly decreased cell proliferation capacity (P<0.01), as well as notably lowered cell invasion and migration capacities (P<0.01). Dual luciferase reporter assay indicated that miR-940 might bind with specific sequences in the 3’UTR of CXCR2, thus evidently suppressing luciferase activity (P<0.01); meanwhile, up-regulating miR-940 would result in apparently reduced CXCR2 protein expression in cells (P<0.01). Conclusion miR-940 expression is down-regulated in breast cancer, which can target CXCR2 to suppress breast cancer cell proliferation, invasion and migration.