In the year 2023, the survival of breast cancer patients is relatively increase and become the leading cause of cancer death worldwide. The early diagnosis of metastatic breast cancer is usually detected by mass of tumors or clinical examination. Once cancer starts to metastasize, the disease carries the worse prognosis and greater decrease of patient survival. In this study, we performed the experiments by using a microarray to compared low (MCF-7) and high (LM-2) metastatic breast cancer cells. we found the increasing of Cardiac Ankyrin Repeat Protein (CARP) level in LM-2 cells. Then we did both overexpression and knockdown of CARP protein in MCF-7 and LM-2 cells, respectively. The results showed that in CARP-overexpressing cells, the ability of cell migration and invasion was increase, while CARP-knockdown cells were reduced. These studies demonstrated that CARP protein is essential for both cancer migration and invasion. For In vivo studies, we did subcutaneous and tail vain injection of CARP-knockdown and control cells in NOD.SCID mice, the results showed less of cancer metastasis from primary to secondary site after injected CARP-knockdown cells. We performed immunohistochemistry using human breast tissue array and found high grade of tumors expressed high levels of CARP compared to low grade. To elucidate the underlying mechanism of CARP protein, we performed Next-Generation Sequencing, mass spectrometer and immunoblotting in CARP-knockdown and control cells. The results indicated that the NF-κB acts as a downstream of CARP protein. The present studies reveal an aspect of the precise molecular mechanism of CARP protein in cancer metastasis. These findings suggesting that CARP protein might be a candidate biomarker as well as targeted therapeutic for metastatic breast cancer.