Objective:To investigate the relationships between the expression level of human epidermal growth factor receptor 2 (HER2) in HER2-positive breast cancer and the characteristics of ultrasound imaging and mammography.Methods:The imaging data of 486 patients with HER2-positive breast cancer treated in the Harbin Medical University Cancer Hospital from January 2014 to December 2021 were retrospectively collected. The relationships between the expression level of HER2 and the imaging features of breast ultrasound and mammography were analyzed.Results:49.38% (240/486) of HER2-positive breast cancer patients were HER2 2+, and 50.62% (246/486) of HER2-positive breast cancer patients were HER2 3+. The age of HER2 2+ patients [ (52.88±1.16) years] was older than the age of HER2 3+ patients [ (49.59±1.00) years], and there was a statistically significant difference ( t=18.07, P<0.001) . There was a statistically significant difference of menstrual status between HER2 2+ patients and HER2 3+ patients ( χ2=4.42, P=0.036) . There were statistically significant differences in the ultrasonography showed burr sign ( χ2=8.37, P=0.010) , posterior echo ( χ2=9.68, P=0.017) , axillary lymph node enlargement ( χ2=15.77, P<0.001) between HER2 2+ patients and HER2 3+ patients. There was a statistically significant difference in the mammography showed whether there were lumps between HER2 2+ patients and HER2 3+ patients ( χ2=15.81, P<0.001) . Conclusion:The expression level of HER2 in HER2-positive breast cancer patients is related to burr sign, posterior echo, and axillary lymph node enlargement shown by ultrasound, as well as lumps shown by mammography, which can provide certain information for clinical prediction of malignant degree of breast cancer, prognosis and individualized treatment plan.