Abstract: There is great value and potential in developing forest biomass energy in China. But at present our development of such energy is still at the preliminary stage and the method of classifying and assessing the total volume of the energy needs further modification and unification. Based on the definition of forest biomass energy and its main sources, this paper provides a classification of forest biomass energy and then analyzes the amount and availability of each constituent of the energy using the latest data of forest assessment of China as well as a bottom-up estimation method.