NOVELTY - The method involves absorbing (20) water and drying the grinded wooden material by a water absorptive material. The livestock dung mixed in the wooden material is fermented (40). The purification gas is supplied (50) after exhaust gas treatment to the wooden material by electricity generation by biomass, to dry the predetermined moisture content. The water absorptive material and the wooden material are laminated alternately in multiple stages, to cover the wooden material by the water absorptive material.    USE - Method for pre-processing biomass fuel for electricity generation.    ADVANTAGE - The efficiency of electricity generation by biomass is improved, and the combustion efficiency is improved. The long term storage is achieved by the water absorption drying process. The drying time of biomass fuel is adjusted arbitrarily.    DETAILED DESCRIPTION - The total ash content of wooden material and the livestock dung is lesser than 0.2 with respect to total fuel weight, and is lesser than 0.15 after mixing process. The total fuel containing chlorine concentration of the wooden material and the livestock dung is lesser than 500ppm, and is lesser than 100ppm after mixing process. An INDEPENDENT CLAIM is included for a biomass fuel pre-processing system has a water absorption drying unit for absorbing water and drying the grinded wooden material by the water absorptive material. A fermentation-drying unit is provided to mix and ferment livestock dung in the wooden material. The exhaust heat drying unit is arranged to supply the purification gas after exhaust gas treatment to the wooden material by electricity generation by biomass, to dry the predetermined moisture content. The biomass fuel produced by the biomass fuel pre-processing system is burnt by a combustion unit. The heat energy of the combustion unit is transformed into electricity by an electric power generation unit.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating the process of pre-processing biomass fuel. (Drawing includes non-English language text)    Step for grinding wooden material (10)    Step for absorbing water and drying grinded wooden material by water absorptive material (20)    Step for mixing livestock dung in wooden material (30)    Step for fermenting livestock dung mixed in wooden material (40)    Step for supplying purification gas after exhaust gas treatment to wooden material by electricity generation by biomass, to dry predetermined moisture content (50)