Abstract: Owing to the difficulties in extracting iris edge image, a new iris location algorithm using geometric symmetry feature and edge detection from gray scale image is presented. Based on this idea, the improved Sobel detector is used to extract iris edge. Geometric features of circle and voting scheme are used to search the iris circle center, then the iris interior and exterior radii are detected by using radius histogram of Hough transform. Results show that the method can improve location speed and is not sensitive to noise effect.