Introduction Mammography and ultrasound are two of the most commonly used and practical tests in breast surgery. When we prescribe breast ultrasound and mammography in the outpatient clinic, one of the most common questions asked by patients is, which is better, ultrasound or mammography? Which one can see more clearly? Is it enough to do one of these tests? In fact, ultrasound and mammography are two completely different examinations: ultrasound has its own advantages in evaluating localized microstructures, and mammography has its own advantages in screening for breast cancer, and they can complement each other in many aspects. For example, molybdenum is more sensitive to calcified foci, while ultrasound has a unique advantage in the diagnosis of cysts. Below I will describe in detail the features and differences between these two tests. I. Mammography The application of mammography is a milestone event in breast surgery. Due to the wide application of mammography, a large number of early breast cancers with no clinical symptoms have been detected in advance, and the mortality rate of breast cancer has been greatly reduced as a result. Mammography has a unique advantage in the early detection of breast cancer, especially in the absence of a mass, which appears only as a calcified spot or a localized structural distortion on the mammogram. In clinical practice, mammography is an important tool for breast cancer screening, and it is recommended that women over the age of 35 have their mammograms taken once a year. The screening age should be advanced for patients with a family history of breast cancer. For patients with diagnosed or suspected breast cancer, a double breast mammogram can help detect multiple or bilateral breast cancers. Regular mammograms are also needed after treatment of benign and malignant disease. Mammography can also be used for localized biopsy of lesions that do not have a mass in the clinic (e.g., calcified foci). Under the supervision of Mammography, a localized guidewire is placed near the lesion, and the lesion is accurately excised according to the position of the guidewire during the operation, which reduces trauma and improves the diagnostic accuracy at the same time. The radiation dose from the mammogram is very low, and the carcinogenicity rate for adult women is similar to the natural incidence rate. For women under 35 years old, due to dense breast tissue, if there is no high risk of breast cancer, it is generally not recommended to undergo mammography. Breast ultrasound Compared with mammography, ultrasound has no radioactive damage and is suitable for any group of people, especially young women and women during pregnancy, and can be performed several times. Ultrasound has certain value in the diagnosis of most benign and malignant diseases of the breast, and it has unique advantages in the diagnosis of breast cysts. Examination of the axillary and upper and lower clavicular lymph nodes is also a strength of ultrasound. Experienced ultrasound surgeons are able to detect microscopic tumors that are not palpable. Ultrasound-guided puncture localization or biopsy of microscopic lesions has become an important tool in breast surgical biopsy, greatly improving accuracy and reducing the number of open surgeries, while many of these lesions do not show up or do not show up well on mammography. At present, many studies have shown that due to the dense breast tissue of Asian women, and the age of breast cancer is earlier than Westerners (the peak of breast cancer incidence in Europe and America is after menopause, the breast tissue is atrophic and thin, and the lesions are shown more clearly on the molybdenum target; whereas the peak of breast cancer incidence in Asians is before menopause, at the age of 40-45 years old, the breast tissue is dense, and the lesions are poorly shown on the molybdenum target), ultrasound has shown more and more important roles in the screening and diagnosis of breast cancer. Ultrasound plays an increasingly important role in breast cancer screening and diagnosis. One more point should be emphasized that, due to its operation characteristics, the results of ultrasound have a great relationship with the machine and the doctor’s experience, and there is a certain rate of leakage and misdiagnosis (in fact, this is the case for any examination), which is normal. Therefore, we should not be superstitious about the examination, and we should combine the physical examination and these auxiliary examinations for a comprehensive evaluation, and we also need regular review and follow-up. Only in this way can we improve the diagnosis rate of early breast cancer, and thus, further improve our treatment results and improve the prognosis of patients.