NOVELTY - The method comprises mixing a wood fiber biomass raw material dried in air with an alkalescent solution at a room temperature for preimpregnating, subjecting the wood fiber biomass and impregnation liquid to stewing pre-treatment at 160-190 degrees C for 30-60 minutes, subjecting slurry to two sections of defibrination, cleaning the slurry with water and stored in a cold place at a millstone clearance of a first section of 0.3-0.4 mm and a second section of 0.1-0.15 mm, adding cellulase into stewed slurry for enzymolysis, and adding water for adjusting the enzymolysis liquid-solid ratio.    USE - The method is useful for pretreating enzymatic saccharification biomass.    ADVANTAGE - The method is capable of simply, effectively and reliably pretreating the enzymatic saccharification biomass with high yield and reduced energy consumption in a safely and controlled manner.    DETAILED DESCRIPTION - The method comprises mixing a wood fiber biomass raw material dried in air with an alkalescent solution at a room temperature for preimpregnating, subjecting the wood fiber biomass and impregnation liquid to stewing pre-treatment at 160-190 degrees C for 30-60 minutes, subjecting slurry to two sections of defibrination, cleaning the slurry with water and stored in a cold place at a millstone clearance of a first section of 0.3-0.4 mm and a second section of 0.1-0.15 mm, adding cellulase into stewed slurry for enzymolysis, and adding water for adjusting the enzymolysis liquid-solid ratio to 15:1 to 20:1 ml/g for obtaining an enzymatic sacchariferous liquor. A dosage of the cellulase relative to oven absolute dry quality of the slurry after defibrination is 15-20 floating-point unit (FPU)/g. The alkalescent solution is a mixed solution of sodium hydroxide and sodium sulfite. A dosage of the sodium hydroxide (1-3%) and sodium sulfite (8-12%) is based on the absolute dry quality of the wood fiber biomass. The liquid-soild ratio of the alkalescent solution to the absolute dry quality of the wood fiber biomass is 2.5:1 to 5:1 ml/g at a predipping time of 8-12 hours. The enzymolysis technique is carried out at a temperature of 45-50 degrees C for 48-60 hours and an initial pH of 4.5-5. The wood fiber biomass comprises gum wood or bagasse.