AIM:To analyze the etiology and the treatment of sudden high intraocular pressure (IOP) during phacoemulsification.METHODS:Three of 408 cases (557 eyes) with cataract suffered high IOP during surgery were treated by intravenous drip of 200g/L mannitol. Two cases(2 eyes) with hypertension lowered the blood pressure. The corrected visual acuity, IOP and corneal edema of postoperative 1day, 1 week were recorded.RESULTS:The IOP of 1 case (1 eye) with capsular block syndrome and 2 cases (2 eyes) with infusion misdirection syndrome decreased after treated by medicines. All the 3 cases successfully completed the phacoemulsification surgery and intraocular lens implantation. 3 cases had better postoperative corrected visual acuity and normal IOP. The classification of corneal edema was level 2 at postoperative day 1 and level 0 at postoperative 1 week.CONCLUSION:Intravenous drip of hyperosmotic agent is an effective treatment to decrease the high IOP during surgery.