The remote sensing image is susceptible to the clouds and fog. In order to improve the output quality of low contrast image and maintain the details, an image enhancement algorithm based on Gaussian mixture modeling (GMM) is proposed. The histogram of original image is smoothed with a 1×3 filter. The best parameters of GMM is got by fitting the histogram with the expectation maximization (EM) algorithm, and the histogram is separated into sub-histograms based on the optimal intersections. The mapping of output image is got according to the Gaussian parameters, and the final enhanced image is obtained. Results of experiments show that the algorithm can determine the optimal number of clusters adaptively and improve the speed of the histogram fitting which costs 0.37 s averagely. Comparing with traditional methods, the enhancement result is superior in terms of objective evaluations of related information entropy and texture information. It can improve the contrast of the remote sensing image while maintaining the details effectively.