Abstract: In the actual coal preparation production, the dry and wet conditions of raw coal itself and the influence of moisture, rain, spraying, washing, etc. lead to different water content on the surface of coal and gangue, and the characteristics of coal gangue images change greatly. The experiment scheme was designed and an image acquisition system was built to establish image sample libraries of coal and gangue in seven different states from saturation to dryness. Nine kinds of characteristic parameters with large differences in the characteristics of coal gangue images in the dry state were selected, and the values of each parameter under different external moisture contents were extracted and analyzed. With the increase of water content, the characteristic parameters of coal and gangue images show obvious changes, and the change of water content has more influence on gangue images than coal..The image characteristic parameters obtained from the test are normalized, and the deviation value of the same characteristic parameter of coal and gangue is compared with the change law of water content. In the texture features, the deviation of the contrast and homogeneity between coal and gangue is most affected by the change of water content. In the whole range of water content change, the parameters with larger deviation between coal and gangue are contrast and homogeneity. The study of the influence of different external moisture on the feature parameters of coal and gangue images provide basic data and reference for the accurate identification of coal and gangue images under working conditions.