With the promotion of functional surgery and minimally invasive surgery, the concept of treatment for giant cystic lesions of the jaws has changed considerably. For cysts of the jaws, especially keratotic cysts and enamel cell tumors of the mandible, the treatment used to be mainly scraping, and even osteotomy was required in severe cases. These surgical methods have disadvantages such as large trauma and easy to leave cystic epithelium, which are no longer used as the preferred treatment for giant cysts of the jaws, but gradually replaced by open window decompression. Open window decompression of maxillary cyst is to open a window on the surface of cystic lesion, open the bone and cyst wall locally, drain out the cystic fluid, and make a stopper to keep the drainage port open, so that the pressure inside and outside the cystic cavity is kept in balance, and under the functional activity of jaw bone, the cystic cavity is gradually reduced and the shape is restored by the new bone around the cyst. Usually the decompression time after open window surgery is 6-18 months, and those whose cysts disappear completely after decompression do not need 2-stage surgery, and those whose cysts do not disappear completely can have 2-stage surgery to scrape out the reduced cysts. The purpose of open window decompression is not to immediately eradicate the cyst directly, but to reduce the cavity, restore the shape of the jaw, and maximize the protection of the morphology and function of the jaw.