Under normal physiological conditions, IGF-1 (insulin-like growth factor-1) has important biological effects. However, many studies have found that IGF-1 is closely related to the occurrence and development of breast cancer. But up to now, the cellular properties of IGF-1 have not been systematically explored in breast cancer cell. It is well-known that the cellular properties and behaviors of IGF-1/IGF-1R are closely related to its biological functions. In the current study, we used the breast cancer cell line as a model to explore the biological characteristics of IGF-1/IGF-1R, and found that IGF-1/IGF-1R can be internalized into the cytoplasm. In addition, we also found that IGF-1R can also enter cell nuclei under the mediation of IGF-1. Further research found that the nuclear-localized IGF-1R has important potential biological effects, which is closely associated to the proliferation of breast cancer cell, this may be achieved by regulating IGF-1R-mediated intracellular signaling. The current research has laid the foundation for investigating the relationship between IGF-1/IGF-1R system and the occurrence and development of breast cancer.