The traditional way of iris location is to extract the iris edge considering it as an ideal circle. To solve the problem that the inner edge of iris is actually not an ideal circle and the outer edge is blurred, a new way to extract the iris edge is proposed in this paper. It firstly unfolds some certain area in iris to a rectangle shape using the pole coordinates transformation, then searches the real inner iris edge according to the steps of grayscale in this rectangular area and finally takes advantages of linear location in this rectangular area to locate the outer iris edge instead of location of that in the human eye images. This method not only solves the problem of pupil carry-over or the texture loss caused by that the inner edge is not an ideal circle but also sharply reduces the location time since it constitutes the point and line detection to the circle detection. Testing on the CASIA-IrisV3 database, the results show that the proposed method costs an average time of 0.172 s and the correct rate is 99.35%.