Abstract: For poor images captured by coal mine video monitoring system with low contrast, uneven illumination and a lot of noise, a single scale Retinex algorithm based on simultaneous denoising of weighted guided filtering was proposed for underground image enhancement. Firstly, low-frequency components of an image are estimated by the weighted guided filter, which replaces Gaussian filter in single scale Retinex algorithm. Secondly, high-frequency components of the image are denoised by the weighted guided filter. Finally, an enhanced image is obtained through conversion from log domain to real field. The subjective visual effect and objective evaluation results show the algorithm has better visual effect and higher image processing speed than traditional image enhancement algorithms.