Filter functions play a significant role in image processing. The traditional implementation method takes the window as the processing unit, whose size is so small that the pipeline is interrupted frequently. This paper proposes an optimization method of algorithm slicing to settle this problem. First, the filtering algorithm is sliced so that each slice processes one pixel in the filter window. Then, the effective processing range is calculated from the position of the pixel in the filter window to remove the complex conditional judgment of the edge of the image. Finally, the software pipeline is carried out in the column direction, allowing the pipeline to repeat a large number of identical instruction sequences. Combined with BWDSP 1042 special instructions and hardware logic, the median filter and other image filtering functions are optimized. The experimental results show that the performance of the entire image filtering functions is improved by more than 51 times in the four-cluster pipeline mode.