Abstract: A formula for evaluating the chemical exergy of structurally complicated materials is presented, and which is derived from the calculation model of real combustion processes. It is simpler in use and wider in application than those given in past published literatures.With the consideration of domestic coal, the average value of the specific entropy from 44 types of coal ash and their correlated formula for estimating the heating values of coal are given therefore, the work done has laid a substantial foundation for the evaluation of the chemical exergy in structurally complicated materials.