To evaluate the clinical value of color Doppler ultrasound combined with plasma miR-21 and miR-27a in the diagnosis of breast cancer (BC). 129 patients with BC and 50 patients with benign breast lesions were selected. They were scanned by color Doppler ultrasound on the breast. The relative expression of miR-21 and miR-27a in plasma was detected by real-time fluorescence quantitative PCR. The clinical value of color Doppler ultrasound combined with plasma miR-21 and miR-27a in the diagnosis of BC was analyzed retrospectively. Two-dimensional ultrasound images of BC showed irregular shape, unclear boundary, burr-like edge, uneven internal echo, weakened rear echo, microcalcification, aspect ratio > 1 and axillary lymph node metastasis. The grade of blood flow signal was improved, mainly in grade II and above, which was statistically different from that of benign control group (P < 0.001). The relative expression of plasma miR-21 and miR-27a in breast cancer group was significantly higher than that in benign control group (P < 0.001). The relative expressions of plasma miR-21 and miR-27a in breast cancer group were significantly correlated with histological grade, clinical stage, lymph node metastasis and postoperation. The relative expression levels of miR-21 and miR-27a in plasma of patients with low histological grade (grade III), high clinical stage (stage III, IV) and lymph node metastasis before operation were significantly higher than those in patients with high histological grade (grade I, II), low clinical stage (stage I, II) and no lymph node metastasis after operation (P < 0.01). The sensitivity, accuracy and negative predictive value of ultrasound combined with plasma miR-21 and miR-27a in the diagnosis of BC were significantly higher than those of each single examination. Color Doppler ultrasound combined with plasma miR-21 and miR-27a can significantly improve the diagnostic efficiency of BC, which is beneficial to early diagnosis and early clinical intervention.