For personal identification based on imperfect irises,accurate iris segmentation is helpful to the feature extraction,classification and identification. The integral-differential method can be used to locate the iris boundaries in eye-images under different illumination cenditions. Iris boundary localization based on integral-differential method is modified to improve the localization success rates and the localization speed by eliminating light spots interference and using pupil the position estimation. Simulation results show that the modified algorithm is effective for iris boundary localization under different illumination conditions.