Breast cancer with low expression of human epidermal growth factor receptor 2 （HER2） has unique biological behaviors. Compared with HER2-zero breast cancer, there are significant differences in molecular subtype and gene expression between the two categories of breast cancer. Novel antibody-drug conjugates represented by T-DXd provide a new treatment option for patients with HER2-low breast cancer, and relevant clinical trials are continuing. At present, the relationship between HER2-low status and prognosis of breast cancer patients remains controversial. In-depth research into HER2-low breast cancer will help further improve clinical outcomes for this population.