High-speed relative motion between the imaging system and the object scene in the duration of the exposure will lead to a radiate blur from image center to image edge, which reduces effective angular field. The captured images are blurred more seriously with the increase of relative motion velocity. The blurred image makes object detection and recognition extremely difficult. The purpose of this paper is to give a degradation model for high-speed relative motion blur, and to analyze the degradation of special circular symmetric images, and factors that affect radiate degeneration, including relative motion velocity, distance between target and camera, and frame frequency. The proposed model explains the phenomenon that the farther from the image center, the more serious the blur becomes. Based on theoretical analysis, the degradation model of practical discrete imaging process is studied. Blurred gray values of the discrete pixels can be obtained along the blurring paths, which are a series of lines pointing at the image center. The radiate degenerate image is simulated finally.