Abstract: Objective To investigate the expression of ADAM12L protein and its nucleic acid in basal-like breast cancer and analyze its clinical significance. Methods The expression of ADAM12L protein in 86 cases of basal-like breast cancer and 20 cases of benign mammary fibroma were detected by immunohistochemistry. The real-time PCR method was used to detect the expression of ADAM12L mRNA in 60 cases of basal-like breast cancer tissue and adjacent tissue. Results Immunohistochemical staining showed that the expression of ADAM12L protein (84.9%, 73/86) in basal-like breast cancer tissues was significantly higher than that in benign breast tissue samples (45%, 9/20), P<0.05. The positive rate of ADAM12L in patients without lymph node metastasis was 47.8%, it's lower than 73.8% the rate of the patients with positive lymph node metastasis (χ²=5.073, P=0.024). In clinical stage Ⅲ-Ⅳ, the positive rate of ADAM12L (74.5%, 41/55) was higher than that of clinical stage Ⅰ-Ⅱ (35.5%, 11/31), χ²=11.073, P<0.01. With real-time PCR, the expression level of ADAM12L in basal-like breast cancer tissues was 2.07±0.95, which was significantly higher than that in adjacent tissues (P<0.05). Conclusion The expression of ADAM12L protein and nucleic acid in basal-like breast cancer tissues is significantly higher than that in normal or benign breast tissues, and is closely related to lymph node metastasis and clinical stage. ADAM12L may be used as a new target for individual diagnosis and treatment of the basal-like breast cancer patients.