Based on the structure of retinal blood vessels and the features of the optic disc（OD）,a fast automatic method of optic disc localization is proposed.In this method,first,the vertical coordinate of the OD is determined according to the distribution structure of the retinal blood vessel network.Then,the horizontal coordinate is located based on the OD brightness information and the relationship between the OD and the blood vessels.Finally,the OD is limited in a small window with the rough location of the OD as the center,and the OD center is precisely positioned via the Hough transform.By this method,neither prior segmentation of retinal blood vessels nor algorithm training is required.Experimental results indicate that the proposed method is of high localization accuracy and speed.