Abstract: Mitochondrial fusion protein 2（Mfn2）is a highly conserved transmembrane GTP enzyme， which is encoded by a newly identified tumor suppressor gene Mfn2. The antitumor effect of Mfn2 is associated with the mitogenactivated protein kinase（MAPK）signaling pathway. MAPK is a major downstream tributary of Ras signaling pathway， which plays an important role in the malignant cells， leading to the tumor invasion and metastasis. In this review， we focus on the recent discoveries on the mechanisms involved in the regulation of Mfn2 and the relationship between Mfn2 and RasMAPK signaling pathway in breast cancer.