Objective To evaluate the application of carbon nanoparticles suspension injection to the axillary lymph node dissection in breast cancer. Methods Sixty-four patients with breast cancer were divided into two groups, one group was given carbon nanoparticles suspension injection before operation, the other was blank control group. All patients received modified radical mastectomy. Lymph nodes were collected and recorded for pathologic examination. Results In the carbon nanoparticles group, lymph nodes and lymph tracts staining were found in the surgery, with an average lymph node detection number of 27.4±5.7 per patient. In the control group, the average number was 21.1±4.2. The difference between the two groups was statistically significant (P＜0.001). In the carbon nanoparticles group, the black staining rate of lymph nodes under naked eye was 84.6% (741/876). The rate of metastasis in black lymph nodes was 33.6% (249/741), in unmapping lymph nodes was 39.3% (53/135). There was no statistically difference between the two groups (P＝0.257). Conclusion Carbon nanoparticles suspension injection is helpful for axillary lymph node dissection and evaluation of metastatic status of the axillary lymph nodes in breast cancer.