Mucus cysts occur in the submucosa of the oral cavity, often the size of a soybean, with clear edges, in the form of small transparent vesicles, and painless. In the submucosa of the oral cavity, there are hundreds of small salivary glands that can secrete colorless mucus, called mucus glands, with the most distribution on the lower lip, soft palate and ventral surface of the tongue. Their excretory ducts open in the oral cavity, and due to trauma to the excretory ducts, mucus leaks out and forms cysts. They are commonly found on the lower lip and mostly occur in those who have the habit of biting their lips. The cyst is located in the submucosa and is a translucent vesicle with a normal mucous membrane covering the surface, which can disappear after a few days due to friction from food, etc. But it can appear again soon, and after several recurrences the mucous membrane produces scar tissue, turning the translucent vesicle into a white hard nodule. Mucous cysts can occur in all age groups, with the most common in people between the ages of 10 and 25, and are equally likely to occur in men and women. The most common type of salivary gland cyst is the minor salivary gland mucous cyst, which is found in the abdomen of the tongue and lower lip. The treatment of this disease is better with surgery, which should remove the affected gland at the same time, because the cause of the disease is damage or obstruction of the glandular duct, and if there is a damaged gland left after surgery, it is inevitable that salivary retention will occur again and the cyst will recur. The main prevention of this disease is to avoid injury and trauma and to maintain oral hygiene.