Abstract: In view of characteristics of darker monitoring image, lower contrast ratio and poor visual effect caused by bad environment of intensive coal powder and weak illumination in coal mine underground, the paper put forward an algorithm of image enhancement based on wavelet transformation and fuzzy theory. The algorithm choses way of wavelet transformation to decompose image, then used new fuzzy membership function and enhancement operator to process high frequency information and used histogram equalization to process the low-frequency information, and finally reconstructed the image. The process results showed that more details information of the image was enhanced and the image effect was improved as a whole.