OBJECTIVE： To discuss the association between ABCB1 gene polymorphisms and adriamycin and cyclophosphamide （AC） combined with chemotherapy-induced severe neutropenia in patients with breast cancer. METHODS： 218 breast cancer patients receiving AC combined with chemotherapy were selected from our hospital during 2012-2015； PCR-RFLP was used to detect polymorphisms of ABCB1 2677G＞T/A and 3435C＞T. The associated between different age， BMI， clinical stages genotypes， etc and AC combined with chemotherapy-induced severe neutropenia were investigated， and risk factors of neutropenia were analyzed by multivariate logistic regression. RESULTS： Among 218 breast cancer patients， 170 patients suffered from severe neutropenia， accounting for 78.0％. Among ABCB1 2677G＞T/A polymorphisms， distribution frequency of GT or GA genotype， TT， TA or AA genotype， GG genotype in severe neutropenia were 80.6％， 86.2％ and 60.0％， with statistical significance （P＜0.05）. Among ABCB1 3435C＞T polymorphisms， distribution frequency of TT， CT and CC genotype in severe neutropenia were 86.4％， 78.4％ and 72.7％， there was no statistical significance （P＞0.05）. AST and ABCB1 2677G＞T/A polymorphisms were correlated with severe neutropenia （P＜0.05）， and ABCB1 2677G＞T/A polymorphism was a strong predictor of neutropenia [OR＝3.875，95％CI（1.555，9.922），P＝0.008]. CONCLUSIONS： ABCB1 2677＞T/A polymorphisms may be aggravate AC combined with chemotherapy-induced neutropenia in patients with breast cancer.