To observe the damage of 23-Gauge and 20-Gauge vitrectomy system to lens. METHODS:Between August 2009 and July 2010, 95 eyes of 91 patients suffered vitrectomy surgery.All paients were phakic. Group A contained 48 eyes of 46 patients who underwent 20-Gauge vitrectomy system.Group B contained 47 eyes of 45 patients who underwent 23-Gauge vitrectomy system. Ceiling lamp was used in 23-Gauge vitrectomy system.Epiretinal membranes peeled,retinotomy, retinal detachment attached, foreign bodies removed, retinal laser photocoagulation, air-fluid exchange, gas or/and silicone oil tamponaded and other steps were taken as needed. Whether the lenses would be damaged in the surgery was observed. RESULTS:In 20G vitrectomy group, 18 eyes had lens damaged while in 23G vitrectomy group, 5 eyes had lenses damaged,P＜0.01. CONCLUSION:23-Gauge vitrectomy system can change the tube position flexibly if necessary,reducing the damage caused by the devices during the opposite base vitreous body vitrectomy.