Objective To approach the feasibility and reliability of mastoscopic axillary sentinel lymph node (SLN) biopsy and axillary lymph node dissection. Methods By using methylene blue to test the axillary sentinel lymph node, endoscopic axillary sentinel lymph node biopsy and axillary lymph node dissection were performed in 36 patients with breast cancer, and adenomammectomy was performed to all the patients. Results Among the 36 patients, the SLN detection rate was 97.22% (35/36), the sensitivity was 92.86% (13/14), the accuracy rate was 97.14% (34/35), the false negative rate was 7.14%(1/14). The average ALN number was 16.14. Conclusions Mastoscopic axillary sentinel lymph node biopsy and axillary lymph node dissection are accurate and reliable with little complication. It is easy to use in clinic.