Abstract： Breast cancer is one of the malignant tumors with high incidence in the world.Clinical practice primarily re-lies on the different expression of human epidermal growth factor receptor 2(HER2)and estrogen receptor(HR)to deter-mine its molecular subtypes,which further guide the selection of treatment options.Previous diagnostic criteria for HER2 in breast cancer patients just classified them as HER2 positive or HER2 negative.However,with the development and ad-vancement of treatment methods,there is increasing attention on the refinement of HER2 subtyping.The concept of HER2 low-expression was also introduced into the breast cancer diagnosis and treatment guidelines in 2021 for the first time.This article aims to conduct a systematic review on the clinical characteristics,treatment status,and future prospects of patients with HER2-low expression breast cancer,in order to better understand the clinical characteristics of the subtype"HER2-low expression".It is intended to provide a scientific foundation for the diagnose and precise treatment of breast cancer patients.