Fisheye lens as an image sensing is for extensive field such as navigational fixing of a mobile robot or an intelligent vehicle and so on. Since a fisheye imaging with wide visual angle can result serious image distortion especially at the image edge, so it is required to be corrected. The center and radius of a fisheye image should be determined before conversion from a fisheye image to a perspective image. Therefore, a method using least square fitting circle is presented in this paper to calibrate the center and radius for images of a fisheye lens, also a cylinder projection model is established to correct a fisheye image. The experimental results prove validity of the proposed methods.