Objective  To study the safety and efficacy of treatment using a pupil dilator during phacoemulsification for a small pupil cataract with a 2.2 mm coaxial microincision. Methods  A total of 32 consecutive patients （40 eyes） with a small pupil cataract were enrolled in this retrospective study and underwent coaxial microincision cataract surgery using the Graether pupil dilator. Postoperative vision， corneal edema， anterior chamber reaction， pupil changes and complications were observed after surgery. Results  The mean pupil size was 5.5-6.5 mm during surgery and all surgeries were completed successfully. There were no cases of iris damage or posterior capsular rupture. Visual acuity was 1.0 or better in 15% of eyes （6 eyes） at 1 month after surgery， 22 eyes （55%） were 0.5-0.8， 11 eyes （28%） were 0.1-0.4， and only 1 eye （2%） was 0.05. Pupil shape was round or approximately round and all pupils had a light reflex during the follow-up period after surgery. Conclusion  The treatment for a small pupil cataract using a pupil dilator during phacoemulsification with coaxial microincision cannot only maintain a sufficient surgical field but also protect the iris， result in good postoperative vision with fewer complications， increases the safety and efficacy of phacoemulsification.