Abstract: o conduct a preliminary study on the tracing effect and influence of a carbon nanoparticle suspension injection in the sentinel lymph node ( SLN ) biopsy of breast cancer. Methods: From June 2009 to June 2011, carbon nanoparticle suspension injections of 0.4 mL to 0.6 mL were injected into the mammary glands of 156 early-metaphase breast cancer patients at 4 to 6 points prior to breast cancer surgery. The lymph nodes were named SLN and non-SLN according their locations relative to the areola. Results: The detection rate of SLN was 97.4%. The false negative and sensitivity rates were 13.3% and 86.7%, respectively. Conclusion: Carbon nanoparticle suspension injections into the mammary gland in SLN biopsy are helpful for accurately evaluating the lymph node condition of breast cancer. The clinical stage, age, primary tumor site, and injection site do not affect the detection and false-negative rates.