Objective To investigate the value of ultrasound-guided diffuse optical tomography(US-DOT)to predict the efficacy of neoadjuvant chemotherapy(NCT)for breast cancer.Methods Fifty-eight cases of breast cancer were treated with NCT were enrolled.Pre- and post-last chemotherapy,the size and total hemoglobin concebtration(HBT)of each lesion were measured by US-DOT.According to the RECIST standard, the lesions were divided into complete response (CR) group, partial response (PR) group, stable disease (SD) group, and progressive disease (PD) group.The analysis of changes of HBT and tumor size before and after NCT in each group；Pearson correlation analyzed the relationship between HBT changes (△HBT%) and tumor size changes (△Size%)；Receiver operating characteristic (ROC) curve predicted the optimal threshold of △HBT% and its diagnostic efficacy for breast cancer neoadjuvant chemotherapy. Results In the above groups, the HBT and size of the lesion after NCT were lower than that before NCT, and the difference between the groups were statistically significant (P<0.001).After NCT,the difference of △HBT% and △Size% were statistically significant in each group(P<0.05).Pearson correlation analysis showed that △HBT% was positively correlated with △Size% (r=0.875).While △HBT%=22.9% as the threshold for prediction of efficiency for NCT,the area under the curve of ROC (Az) was 0.872, and the sensitivity was 82.93%, , specificity was 76.47%, positive predictive value was 72.34%, negative predictive value was 36.36%,and accuracy was 65.52%, respectively.Conclusions During neoadjuvant chemotherapy for breast cancer, US-DOT parameter △HBT% was positively correlated with △Size%.△HBT% can predict the efficacy of neoadjuvant chemotherapy for breast cancer before operation.