Abstract: Objective To explore the value of contrast-enhanced malignancy imaging features in secondary grade diagnosis of Breast Imaging Reporting and Data System for Ultrasonography (BI-RADS-US) Type 4 atypical breast lesions. Method After initial diagnosis by ultrasound (US), 124 BI-RADS-US Type 4 patients with 130 lesions were examined by contrast-enhanced US (CEUS) and were classified again before surgery according to five contrast-enhanced malignancy imaging features: inhomogeneous enhancement, peripheral ring-like enhancement, expansive enhancement, internal filling defects and surrounding radioactive convergence. Lesions with no contrast-enhanced features of malignancy were categorized as Type 3; lesions with one, two or three features of malignancy were categorized as Type 4A, 4B or 4C, respectively; and lesions with four or more indices of malignancy were categorized as Type 5. The value of contrasted imaging features of malignancy in diagnosing BI-RADS-US type 4 atypical breast lesions was analyzed. Result: 130 lesions were confirmed by surgery and pathology, including 67 benign lesions and 63 malignant lesions. BIRADS-US4 A lesions were 61, 41 lesions of 4B, 28 lesions of 4C before CEUS, Grade BIRADS-US3 lesions were 49, BIRADS-US4 lesions were 13, 7 lesions of 4B, 12 lesions of 4C, 49 lesions of 5 grade after CEUS. The sensitivity, specificity, accuracy, positive and negative predictive value of contrast-enhanced ultrasound in the diagnosis of BIRADS-US4 atypical breast lesions were 90.4%, 83.6%, 86.9%, 83.8%, 90.3%,respectively, CEUS decreased the benign lesion biopsy ratio to 68.5% (46/67) and increased the diagnosis ratio of malignant lesions to 73.0% (46/63).Conclusion: Breast malignant tumor imaging characteristics of BIRADS-US4 atypical lesions with high accuracy, in reduce BIRADS-US4 atypical lesions biopsy risk, also can improve malignant lesions diagnostic confidence at the same time, so as to further optimize the BIRADS-US4 atypical breast lesions classification, it can better provides reference basis for clinical diagnosis and treatment BIRADS-US4 atypical breast lesions. It is important to note that a small number of atypical features of contrast-enhanced ultrasound breast cancer lesions need to be cautious when regarding, they should be closely combined with the two-dimensional ultrasound features and suggest puncture biopsy to avoid missed diagnosis.