Breast cancer is one of the most important malignant tumors affecting women’s health. Epigenetic modification and oxidative stress caused by excessive accumulation of reactive oxygen species (ROS) play a key role in the occurrence and development of breast cancer. In addition, epigenetic modification and the production and clearance of ROS interact with each other. In this paper, epigenetic modification and ROS involved in the occurrence and development of breast cancer are reviewed in order to provide possible ideas for seeking biomarkers and precise therapy for the treatment of breast cancer.