Objective: To investigate the relationship between different molecular subtypes of breast invasive ductal carcinoma (IDC) and axillary lymph node metastasis. Methods: According to the molecular classification criteria of breast cancer, the 243 patients with primary breast IDC undergoing surgical treatment were divided into luminal A, luminal B [further subdivided into HER-2 (–) and HER-2 (+)], HER-2 over expression and triple-negative type. Combining with the clinical pathological data, the distribution characteristics of various molecular subtypes, and the relations of different molecular subtypes with axillary lymph node metastasis were analyzed. Results: Among the 243 patients, cases with Luminal B [HER-2 (–)] type accounted for the majority (78 cases, 32.1%), and Luminal A type was the next (58 cases, 23.87%), followed by triple-negative (41 cases, 16.87%), HER-2 over expression (34 cases, 13.99%) and Luminal B [HER-2(+)] type (32 cases, 13.17%), successively. Axillary lymph node metastasis occurred in 94 cases (38.68%), and the incidence of axillary lymph node metastasis was statistically different among patients with different molecular subtypes (P<0.05). It was highest in those with luminal B [HER-2 (–)] (42 cases, 53.85%) or Luminal B [HER-2 (+)] type (15 cases, 46.88%), with no statistical difference between them (P>0.05), followed by Luminal A (19 cases, 32.76%), triple-negative (12 cases, 29.27%) and HER-2 over expression type (6 cases, 17.65%), successively; no significant difference was found in distribution of the molecular subtypes either in group of patients with involvement of 1 lymph node to 3 lymph nodes or ≥ 4 lymph nodes (both P>0.05), although the number of cases with Luminal B [HER-2 (+)] type was highest and HER-2 over- expression type was lowest in the former, while the number of cases with HER-2 over- expression type was highest and Luminal B [HER-2(+)] type was lowest in the latter. Conclusion: In breast IDC, molecular subtype has certain reference value for assessing axillary lymph node metastasis and judging disease status, and it can probably be used as a basis for making individualized diagnosis and treatment strategy.