Based on the accurate analysis of cucumber disease images, the low level feature of images was effectively extracted, and Gaussian Mixture Model (GMM) for 8 common cucumber diseases was built. The parameters of GMM were estimated by the algorithm of expectation maximum (EM) to accurately charac- terize the feature distribution of 8 cucumber diseases, thus increased the correct identification of cucumber diseases and accurate grasping of damage conditions, and provided basis for achievement of real-time and accurate prediction of cucumber diseases.