Objective: The purpose of this study is to explore the relationship between plasma D-dimer level and axillary lymph node metastasis of breast cancer, and to provide the basis for predicting axillary lymph node metastasis. Methods: 73 cases of breast cancer (breast cancer group), 36 cases of benign breast disease (benign breast disease group) and 50 cases of healthy women (normal control) were collected. Plasma D-dimer levels of the three groups were detected. Histopathologic variables (tumor size, pathological type, lymph node metastasis, number of lymph node metastasis, etc.) were classified and analyzed systematically. Results: Plasma D-dimer levels in breast cancer patients are higher than those in benign breast disease group and normal control group, and the differences are statistically significant (P<0.01). The differences of D-dimer levels in benign breast disease group and normal control group are not statistically significant (P>0.05). Plasma D-dimer levels in the positive axillary lymph node metastasis group are higher than the negative axillary lymph node metastasis group, and the differences are statistically significant (P<0.01). Tumor size, pathological type, and the plasma D-dimer levels are associated with the number of axillary lymph node metastasis significantly (P<0.01). Pathological type and plasma D-dimer levels are independent influential factors in axillary lymph node metastasis (OR =7.464, 6.470). Using the cutoff value of 0.455 μg/mL, elevated plasma D-dimer levels had a high specificity of 86.2% and moderate sensitivity of 52.3%. The area under ROC curve for D-dimer values in predicting lymph node involvement is 0.689. Conclusion: Plasma D-dimer levels are correlated with axillary lymph node metastasis status and the number of lymph node involvement. Elevated plasma D-dimer levels have some value in predicting axillary lymph node status in breast cancer.