Bilateral maxillary sinus cysts are very rare and are usually unilateral, most of them are mucinous cysts, which are caused by blockage of the glandular ducts of the sinus mucosa. When the cyst is small, the patient does not have any specific symptoms, but if the cyst is persistently enlarged, it may rupture and cause intermittent flow of yellowish fluid from the nasal cavity, accompanied by a swelling sensation in the face and headache. If the cyst ruptures repeatedly or continues to increase in size, surgery is required because repeatedly ruptured cysts have the potential to become malignant. If the cyst does not increase in size and remains in its original state, surgery is not necessary and regular observation is sufficient.