Abstract： Objective To analyze the correlation between body mass index(BMI)and pathological complete remission(pCR)in human epidermal growth factor receptor 2(HER2)-positive breast cancer patients treated with trastuzumab neoadjuvant chemotherapy.Methods The clinical data of 136 HER2-positive breast cancer patients treated with trastuzumab neoadjuvant chemotherapy from May 2018 to June 2022 were collected.Clinical pathological features of them with varying BMIs were analyzed,and the correlation between BMI and pathological features of HER2-positive breast cancer patients treated with trastuzumab neoadjuvant chemotherapy was identified.Univariate and multivariate logistic regression analyses were performed to identify the correlation between BMI and pCR.Results Among 136 HER-2 positive breast cancer patients,43(31.62％)achieved pCR.The proportions of patients with T staging Ⅲ-Ⅳ,positive progesterone receptor(PR),Ki-67 ≥14,and positive lymph node metastasis in BMI≥24 group were significantly higher than those of BMI＜24 group(P＜0.05).There were no significant differences in the age,menstrual status and Ki-67 level between pCR group and non-pCR group(P＞0.05).The proportions of T staging Ⅲ-Ⅳ,negative estrogen receptor(ER),negative PR,positive lymph node metastasis,and BMI≥24kg/m2 in pCR group were significantly lower than those of no-pCR group(P＜0.05).PR,lymph node metastasis and BMI were the risk factors of pCR in HER-2 positive breast cancer(P＜0.05).Conclusion pCR is correlated with PR,lymph node metastasis and BMI in HER-2 positive breast cancer treated with Trastuzumab neoadjuvant chemotherapy.Concerning the relationship between BMI and clinicopathological features of HER-2 positive breast cancer,BMI is an independent risk factor of pCR in HER-2-positive breast cancer with trastuzumab neoadjuvant chemotherapy.