A fast algorithm for iris localization based on gradient pair detection and randomized circle detection(RCD) is presented.We employed edge detection to generate an edge map.The inner circle detection was to search the gradient pair vectors based on center symmetry rule and to obtain the circle parameters through the Statistic calculating.The outer circle detection used in the proposed RCD is that we first randomly select four edge pixels and define a distance criterion to determine whether there is a possible circle.We applied an evidence-collecting process to localize the outer circle of iris.The Experimental results show that the proposed method has an encouraging performance that shows 98.1% localization success and reduces the system operation time and memory demands.