Abstract: The contents of the major and trace elements in 3 samples of the claystone with different types and textures, from the coal measures of the Taiyuan and Shanxi Formations of Permo-Carboniferous of Xiaoyu coal mine of Datong, Shanxi province, are detected by the methods of chemical analysis and INAA respectively.By the contrast analysis of the elements with geochemical tracer and their ratio, three samples, on geochemistry as a whole, are not of the typical characteristics of sedimentogenic mudstone, and could be formed in situ from the alteration of acidic or alkali-acidic ash (fallout or water-carried) under the conditions of the shallower water and weak oxydation on the surface.The alteration of the claystone is stronger on the whole, and it causes much loss of the unstable elements, even some of more stable elements, such as ferromolybdenum and manganese.The environments, medium conditions and original matter and its size at the ash alteration, as well as the clay minerals of the clay rocks are the major reason of the differences on the types and element contents of the claystones.