Objective To investigate the relationship between serum microRNA-101-3p(miR-101-3p),pol-ypeptide N-acetylgalactosaminyltransferase 1(GALNT1)and the efficacy and prognosis of neoadjuvant chem-otherapy(NAC)in breast cancer.Methods A total of 203 breast cancer patients who underwent NAC in this hospital from January 2017 to August 2019 were selected as breast cancer group.They were divided into the ineffective group and the effective group according to the therapeutic effect of NAC,and divided into the death group and the survival group according to the 5-year survival situation.Additionally,203 healthy women who underwent routine physical examination during the same period were selected as the control group.The clini-cal data and the levels of serum miR-101-3p and GALNT1 were detected and compared.The binding sites of miR-101-3p and GALNT1 were predicted through the online database.Pearson correlation analysis was per-formed to assess the correlation between serum miR-101-3p and GALNT1 expression in breast cancer pa-tients.The relationship between serum miR-101-3p,GALNT1 and the efficacy and prognosis of NAC in breast cancer patients were analyzed by multivariate unconditional Logistic regression and Cox regression.The pre-dictive value of serum miR-101-3p and GALNT1 for the ineffectiveness and mortalit of NAC treatment in breast cancer patients were analyzed by receiver operating characteristic(ROC)curve.Results Compared with the control group,the expression level of serum miR-101-3p in the breast cancer group decreased,and the level of GALNT1 increased,and the differences were statistically significant(P＜0.05).Serum miR-101-3p in patients with breast cancer was negatively correlated with GALNT1(P＜0.05).High expression of Ki-67,≥4 axillary lymph node metastases after surgery and high expression of GALNT1 were independent risk factors for ineffective NAC treatment in breast cancer patients(P＜0.05),and high expression of miR-101-3p was an independent protective factor(P＜0.05).TNM stage Ⅲ,postoperative axillary lymph node metastasis ≥10,and high expression of GALNT1 were independent risk factors for ineffective NAC treatment in breast cancer patients(P＜0.05),while high expression of miR-101-3p was an independent protective fac-tor(P＜0.05).The predictive efficacy of combined detection of serum miR-101-3p and GALNT1 for ineffec-tive NAC treatment and death in breast cancer patients was higher than that predicted by either of them alone(both P＜0.05).Conclusion Low serum miR-101-3p and high GALNT1 expression in breast cancer patients are closely related to NAC efficacy and prognosis.The combination of the two has a high predictive value for both the efficacy and prognosis of NAC.