1. An iris identification system for confirming identity of a person, wherein the iris identification system comprising: a mode converter for selecting one of registration and identification modes; an image input means for inputting an iris image; a luminance adjustment module for sequentially selecting predetermined luminance levels when the registration mode is selected by the mode converter and irradiating the light of the selected luminance level together with infrared ray to the eye for iris registration; a registration module for capturing a plurality of iris images inputted by the image input means whenever the light selected by the luminance adjustment module is irradiated to the eye, preprocessing the captured iris image to decide pupil boundary, pupil center, iris size, and class to which the iris image belongs, defining the preprocessed iris image as main, auxiliary, negative main and compensation data, encoding the defined data, and registering the encoded data as data of the reference iris images; an identification module for capturing an iris image inputted by the image input means when the identification mode is selected by the mode converter, preprocessing the captured iris image to decide pupil boundary, pupil center, iris size, and class to which the iris image belongs, defining the preprocessed iris image as main, auxiliary, negative main and compensation data, encoding the defined data, and analyzing similarity between the encoded data of the iris image for identification and the encoded data of the reference iris images registered in the registration module; a reference iris image storage for storing the data of the reference iris images registered in the registration module; and a main control unit for controlling the image input means, the luminance adjustment module, the registration module, the identification module and the reference iris image storage according to the operation mode of the mode converter.