Chronic dacryocystitis is caused by narrowing and obstruction of the nasolacrimal duct, resulting in retention of tears in the tear sac with bacterial infection. It is often associated with trachoma, lacrimal trauma, deviated nasal septum, and enlarged inferior turbinate. The main manifestations are: overflowing tears or pus, inability to flush the tear ducts, etc. Chronic dacryocystitis is an infection of the eye, which is very harmful to the eye and must be treated as early as possible. Commonly used methods such as: lacrimal duct exploration; lacrimal duct hanging; lacrimal duct placement; lacrimal duct laser; external nasal approach lacrimal sac nasal anastomosis, etc., some of these methods are simple and easy to perform, but the effect is not ideal, easy to recur; some are traumatic, bleeding, postoperative facial scars. The principle of minimally invasive lacrimal sac surgery is to use minimally invasive nasal endoscopic surgical techniques to reconstruct the lacrimal sac and nasal lacrimal drainage channels to achieve the purpose of curing dacryocystitis. Indications for surgery: 1, chronic dacryocystitis, 2, dacryocyst; 3, acute dacryocystitis, dacryocystic abscess, dacryocystic fistula; 4, failed lacrimal laser, tube placement; 5, nasolacrimal duct obstruction; 6, traumatic dacryocystitis; 7, recurrence after extra-nasal lacrimal sac nasal anastomosis. The advantages of minimally invasive lacrimal sac surgery: 1, surgery from the nasal cavity, no facial incision; 2, to avoid surgery damage to the inner canthus blood vessels, ligaments; no need to remove stitches and change drugs after surgery; 3, short surgery time, less trauma, light postoperative reaction, fast recovery, high efficacy; 4, acute dacryocystitis, lacrimal sac abscess without first cut row, change drugs; 5, can simultaneously deal with the accompanying nasal diseases such as nasal septal deviation, nasal polyps etc.