Abstract：Objective：To analyze the changes of ultrasonography in breast cancer before and after neoadjuvant chemotherapy (NAC), and to evaluate the value of high frequency ultrasound in the evaluation of NAC efficacy. Methods： A retrospective analysis of 87 cases of breast cancer patients before and after NAC lesions size, blood flow, and hardness change, and compared with pathological assessment. Results： ultrasound in 6 lesions disappeared after NAC, its degree of sensitivity, specific, the accuracy is 87.5%, 65% and 81.1% respectively; The largest diameter line with residual foci, blood flow grade, elastic score changes as NAC after a review of the efficiency index, evaluation of effective chemotherapy accuracy were 79.2%, 84.9% and 94.3% respectively. The sensitivity of 95.2%, 95.6% and 97.9% respectively. Conclusion： Ultrasound has important value in assessing the effect of NAC of breast cancer, after NAC for ultrasonic elasticity score, blood flow grade evaluation effect index to evaluate residual diagnosis coincidence rate, the sensitivity of the oven is higher than with maximum diameter line for the evaluation of effect index evaluating residual foci, and histologic evaluation of the effectiveness of chemotherapy with high consistency.