The stability of coal seam is an important parameter to determine the type of coal mine exploration, and it is also a reliability index to determine the calculation of the density and reserves of the exploration. With the gradual improvement of the mechanization level of coal mining, the change of coal seam thickness in advance was identified. In the past, quantitative calculation of coal seam stability was mostly based on formula calculation, which involved heavy workload, cumbersome calculation, slow operation and error prone. At present, computers are widely used in mine geological work. C++ language programming was applied to evaluate the stability of coal seam quantitatively. The program was fast and accurate, and the operation was simple. The results of the evaluation would provide reference for the selection of coal mining methods, coal mining technology and support.