A descreening method for scanned image based on FIR digital low pass filter was put forward. The image was converted from the spatial domain to the frequency domain and the frequency domain was processed by FIR low pass filter. The optimal filter parameters were selected combined with image evaluation PSNR. The descreening algorithm was compared with other commonly used algorithms. The result showed that the algorithm has good descreening effect and can better maintain the edge information at the same time.