Abstract: One-step nucleic acid amplification (OSNA) technology is a molecular diagnostic technology that assesses the metastatic status of lymph nodes by detecting the expression level of cytokeratin 19 mRNA in sentinel lymph nodes (SLNs). It is characterized by its rapidity, accuracy, semi-quantitative nature, and high reproducibility, thereby providing comprehensive lymph node diagnostic information for clinical physicians. It is of great significance regarding avoiding secondary axillary lymph node dissection (ALND) or excessive ALND. The de-escalation treatment pattern for breast cancer is the current therapeutic strategy pursued by surgeons. SLN biopsy (SLNB) can help patients receive more precise and personalized treatment, thereby reducing unnecessary treatment intensity and side effects while ensuring therapeutic efficacy. This article reviews the application of OSNA detection in SLNB.