Iris image preprocessing, including iris localization and iris image quality evaluation, is the key step in iris recognition and has a close relationship to the accuracy of matching. So far, there are many iris localization algorithms having been proposed. In this paper, we propose a new iris localization algorithm, in which we adopt edge points detecting and curve fitting. After this, we set an integral iris image quality evaluation system that is necessary in the automatic iris recognition system. All the procedures of the algorithm are proved to be valid through our experiment on 2400 iris images from CASIA (The Institute of Automation, Chinese Academy of Sciences) database.