Abstract: The coal bed stability classification is correct or not, which relates to directly the geological exploration type of coal resources, the exploration effect, the mining face layout and the mining method choice in the mine construction. Based on the analysis of the main factors which affect the coal bed stability, the analysis of the mathematical methods as well as the advantage and disadvantage of mathematical methods applied to quantitative evaluation of the coal bed stability, this thesis has advanced a new idea that is a combination method of the trend surface analysis and the mathematical statistics (that is, the trend and variation method) to the quantitative evaluation of coal bed stability. This idea considers the discrete degree of the different coal bed thickness change and the spatial distribution and relativity of these coal thickness points value.