Abstract: For unclear underground video monitoring image caused by poor light and a lot of dust, an improved non-local means filtering algorithm was proposed. Firstly, video monitoring images are processed by Log edge extraction operator, so as to extract edge information of the images, and edge images and non-edge images are obtained. Then, non-local means filtering algorithm is improved from the perspective of extraction method of similar image blocks and weighting calculation method, and the improved algorithm is adopted to filter noise in the non-edge images. Finally, the edge images and the filtered non-edge images are fused. Median filtering algorithm, average filtering algorithm, non-local means filtering algorithm and the improved algorithm were used to deal with field images. The test results indicate that the improved algorithm has better image processing effect than the other algorithms.