The key points of the motion blur image restoration are the acquisition of the blur angle and length. This paper proposes two methods for improving detection accuracy of the cross bright line impact angle in the spectrum image of the motion blur image. On the basis of Radon transform, the effect of cross bright line pair detection accuracy is reduced by decentralizing the spectrum of the blurred image, and performing secondary Fourier transform to refine the fringe information. After comparative experiments, it was found that the two methods could improve the detection accuracy by about 1° to 3°.