Abstract: Objective To evaluate the value of early application 18F- flurodeoxyglucose（FDG） PET/CT in breast cancer to neoadjuvant chemotherapy;and compare the efficiency on predicting the outcome of neoadjuvant chemotherapy between the changes of maximum standard uptake value(SUVmax) and target organization/non-target organization（T/NT），so as to select suitable index and the specific values to evaluate the therapeutic effect. Methods In a prospective trial, 18F-FDG PET-CT scans were performed in 22 women with primary breast cancer before neoadjuvant chemotherapy and after the first and second cycle of neoadjuvant chemotherapy，and the changes of SUVmax and T/NT were calculated. Results The responder group had a greater decline in SUVmax and T/NT than the non-responder group(P<0.05)at the first cycle,under the ROC curves,the best prediction effect of ΔSUVmax1% was 36.3%(sensitivity 83.3%,specificity 80.0%),the best prediction effect ofΔT/NT1% was 42.8%(sensitivity 83.3%,specificity 86.7%),the best prediction effect of ΔSUVmax2% was 57.7.3%(sensitivity 83.3%,specificity 93.3%),the best prediction effect of ΔT/NT2% was 53.4 %(sensitivity 83.3%,specificity 73.3%),respectively. Conclusion 18F-FDG PET-CT could be feasible to predict the pathological response of primary breast cancer after neoadjuvant chemotherapy at the first cycle，to support the effective patient to continue treatment,T/NT is no better than SUVmax on the neoajuvant chemotherapy efficacy evaluation in our research.