Abstract: The method of establishing the point spread function(PSF) of motion-blurred image is discussed.For linear motion blur,it is proved that the two dimensional PSF must be established directly in the motion direction,instead of decomposing to two axes or rotate to the horizontal axis.Then an algorithm is presented to estimate the two key parameters of PSF: establish the cepstrum of the motion-blurred image and find the minimum of it,the location of the minimum gives the information of blur range and blur direction.Experimental results show that the method can guarantee a small error a good quality of restoration when blur is at arbitrary direction and between 5-55 pixels.A big error occurs when blur range is out of 5-55 pixels.