Auxiliary examinations of the breast mainly include ultrasound, mammography and MRI of the breast. Ultrasound and mammogram are very effective adjuvant examinations, and together with the doctor’s examination, they are called the “golden triad” of breast examination. When a lump is found in the breast, should I choose ultrasound or mammography? I will briefly describe the characteristics of both. Ultrasound is a non-invasive, repeatable examination that is not limited by age or glandular denseness and has the advantage of observing cystic lumps in the breast, as well as the blood flow of the masses. The diagnosis of malignant tumors with sandy calcifications as the main manifestation is not as good as mammography.