Nipple overflow is one of the common clinical symptoms of breast diseases, and about 10% of women can be found to have nipple overflow during routine physical examination. In recent years, the incidence of breast cancer is not only on the rise, but also the incidence of breast cancer is getting younger and it is the first malignant tumor among women. Nipple discharge has a close relationship with breast cancer. It is one of the symptoms of breast cancer. About 10-30% of nipple discharge is caused by malignant lesions in the breast. In 12% of these patients, no lump can be palpated and 10% of them have negative mammograms. Early clinical detection and treatment to clarify the etiology and clinical importance of nipple discharge is essential. In the past, patients with nipple overflow could only be diagnosed by selective mammography, overflow smear, X-ray and ultrasound because they could not visualize the lesions in the ducts, and their diagnostic rates were not high, about 50%-80%, not intuitive and difficult to localize the lesions. Due to the low diagnosis rate, almost all patients opt for surgery, resulting in severe breast deformation, reduction in size, large scarring, asymmetry of both breasts, and psychological damage to women. The application of breast ductal endoscopy not only greatly improves the diagnostic accuracy of the cause of nipple overflow, allowing patients to avoid unnecessary surgery, but also overcomes the shortcomings of mammography and other conventional examination methods that make it difficult to confirm the diagnosis. This makes it possible to observe the lesions and quickly confirm the diagnosis through the naked eye. The biggest advantage of breast ductoscopy is that it can provide early diagnosis, symptomatic treatment and accurate localization of breast diseases, avoiding the blind surgery of traditional therapy. Ductal endoscopy is mainly used for diagnosis and treatment of lesions in the milk ducts. The endoscope is composed of ultra-fine optical fibers and silicone, so it is very soft and non-invasive. It is painless for the patient and relatively easy to insert into the ducts. With a 0.5mm-0.7mm ultra-fine optical fiber, the ductal lesion can be observed approximately 6-7cm from the ductal opening. Depending on the depth of insertion of the ductoscope and the photoelectric reflection on the surface of the breast skin, the lesion site can be clearly identified and the progress of the lesion can be confirmed, which is a guideline for tumor surgery and can determine the scope of surgical excision and the selected surgical method. Under the endoscope, through the combination of ultra-fine optical fiber and biopsy apparatus, cellular tissue can be collected and biopsied for pathological diagnosis. The detection rate of tumors in the milk ducts has been improved, allowing some patients to avoid unnecessary excisional biopsies. For inflammatory milk ducts, pharmacological irrigation can be given and most of them heal with a single irrigation. The misdiagnosis of direct surgical excision due to simple nipple overflow is avoided.