Abstract: For problems of uneven brightness, blurry detail texture and much noise existed in underground video images, and image distortion, unclear image level and low processing efficiency of common image enhancement algorithm used to process underground video image, an underground video image enhancement algorithm based on contrast limited function and feedback function was proposed. Firstly, image is preprocessed with grayscale and denoising by weighted average method and median filtering. Then contrast is enhanced by use of contrast limited function. Finally, gray level is adjusted by feedback function so as to enhance image level. The experimental results show that the algorithm can effectively improve underground video image distortion with clear level and fast processing speed.