This paper deals with the main transformation directions and the affecting factors of kaolinite as well as the main composition of tonstein by studying the petromineralogical features of tonstein intercalations in the anthracite bed. A series of means, such as microscopic identification, differential thermogram analysis, X_ray powder diffraction analysis, infrared absorption spectrum analysis, were used to study the samples collected from the working field. The research results suggest that kaolinite is transformed toward illite, accompanied by the appearance of I/M and montmorillonite. The heightening of the metamorphic grade of coal and the transformation of its sloam are attributed to the action of regional metamorphism and the influence of the surrounding media conditions.