Abstract: The present paper points out that the combustibility of forests may be divided by the quantitative method of biomass and energy of forest.A concrete analysis of the artificial coniferous forests such as red pine,scotch pine and larch forests in the north-eastern China was carried out.The results showed that the quantity and energy of the dangerous combustible materials such as surface litter grass,bush,needle,twig will as diameter less than 1cm,dry branch are the most important basis for dividing the combustibility of forests. This paper also puts forward that the main factors influencing quantity and energy of the combustible materials in forests are topography,age of trees and moisture content of soil. Based on these factors the index of the quantity and energy of the combustible materials of various forests are estimated.