Abstract- Each human is body is created by the god uniquely using various combinations of infinite DNA structure and at all different from others. Even a twin people have some kind of differences in characters and others. Biometric technology exploits this unique property to ensure that it is only one person enlisted for the sake of accessing a system. One type of available biometric techniques is the detection of iris. Iris is an internal organ of eye. This membrane is in the form of ring encircling pupil and gives colour pattern of an eye. There is no one has the same iris structure. Even the irises of left and right eye are different. Here, random pattern slice of iris can be used as passport or a password for a person within his/her lifetime. In this case, the iris image is processed by converting the image into grayscale, and using segmentation and mahalanobis distance is used for pattern recognition.