The invention relates to a method for preparing a high-density biomass fuel for roasting tobacco by tobacco stalks. The method comprises the following steps: smashing, waste tobacco (tobacco stalks, tobacco stems and tobacco leaves) used as a raw material, to obtain 1-2cm, 4-6cm and 8-10cm particle materials; drying the particle materials in a hot blast drying furnace till the water content is 7-16%; feeding dried and mixed particle materials to a stirring heater to heat; and pressing and forming by a forming device, namely a flat-die machine to obtain a product, wherein the product obtained is a solid cylinder with the diameter which is 32mm, the density which is 1.4g/cm<3>, 1.4-1.3g/cm<3> and 1.2-1.3g/cm<3>, and the length-diameter ratio l:d which is 2-6. No chemical additives are added in the preparation process. The density of the biomass fuel prepared by the invention can reach 1.2-1.4g/cm<3>, so that the biomass fuel can meet heat demands for roasting the tobacco leaves in different stages. The capacity for providing heat is better than that of fire coal, and heat provided by unit time is 4 times that of the fire coal.