Objective:To investigate the feasibility of multipoint core needle biopsy (CNB) at mid-stage to predict the treatment effect of neoadjuvant systemic therapy for breast cancer.Methods:A total of 67 breast cancer cases with indications of neoadjuvant systemic therapy were selected from Mar. 2021 to Nov. 2022.In the fourth cycle of neoadjuvant systemic therapy, core needle biopsy was performed at 3, 6, 9, 12 points of tumor bed and residual tumor foci of breast respectively.The results of CNB were compared with the results of routine pathology of surgery after the completion of neoadjuvant therapy. Matched biopsy and surgical specimens were compared to assess pCR. The accuracy and false negative rate (FNR) of interim pathological assessment were analyzed. The coincidence probability of interim biopsy pathology and pathology of standard surgical excision was verified.Results:The median age of enrolled patients was 49.2 years (21-69 years) .Median maximum tumor diameter before neoadjuvant systemic therapy and residual tumor diameter after neoadjuvant therapy were 40.4 mm (range 21-93mm) and 19.6 mm (range 0-41mm) respectively. A total of 28 patients achieved pCR, and the PCR rates of hormone receptor-positive and HER2-nagative,triple-negative,hormone receptor negative and HER2-positive and hormone receptor-positive and HER2-positive disease were 4/24 (16.7%) ,6/14 (42.9%) ,11/18 (61.1%) ,7/11 (63.6%), respectively. Two cases had no preoperative imaging abnormalities. The results of core needle biopsy pathology of residual tumor lesions in 55 patients were consistent with those of routine post-operation pathology.The results of core needle biopsy pathology of tumor bed of 56 patients was consistent with the routine pathology of surgery. The false negative rate of interim multipoint biopsy pathology of residual tumor foci was 17.9% (12/67). The false negative rate of tumor bed with core needle biopsy was 5.9% (4/67) .Conclusions:CNB guided under ultrasound is feasible in predicting tumor retreat situation in the tumor bed area and residual tumor foci at mid-stage of neoadjuvant therapy. Increasing the number of core needles and improving biopsy techniques may improve the accuracy of pathological evaluation of interim multipoint biopsy.