NOVELTY - Pre-acidification of steam-explosion material water washing liquid for anaerobic fermentation to produce marsh gas, by processing waste steam of bamboo involves: adjusting steam water washing solution so that chemical oxygen demand is less than 1300 mg/l for waste water; adjusting nutrients such that Kjeldahl nitrogen is more than 100 mg/l and phosphorus is more than 20 mg/l in waste water, and adjusting pH to 4.5-7; preparing liquid seed by acidifying for 2-14 days; adding mixed solution to seed and solvent; and acidifying solution, where acidifying mixing is 25%.    USE - As pre-acidification treatment method for steam-explosion material water washing liquid for anaerobic fermentation to produce marsh gas (claimed).    ADVANTAGE - The method provides improved acidification and acidification time of water solution that produces marsh gas. The present method uses acidification explosion material water washing liquid as liquid to inoculate acidifying seed, which reduces microorganism adapt to new environment of stopping time, adjusts proper nutrition proportion, controls proper fermentation conditions and beneficial microorganism acidification reaction, such that for steam water washing liquid of acidification, acidifying is more than 25%, acidifying time is less i.e. not greater than 24 hours, and can continuously run anaerobic reactor to produce marsh gas, which is beneficial for industrial production of marsh gas.    DETAILED DESCRIPTION - Pre-acidification treatment method for steam-explosion material water washing liquid for anaerobic fermentation to produce marsh gas, by taking bamboo such as grass or straw raw material and processing waste steam exploded by steam explosion, involves: preparing liquid for the steam-exploded material water washing, to obtain steam-exploded material water washing solution, by adjusting the steam water washing solution so that the chemical oxygen demand (COD) after marsh gas production is less than 1300 mg/l of waste water, where COD in water or mixed solution for acidifying is 2000-20000 mg/l; adjusting the steam water washing liquid nutrient substance containing nitrogen and nutrient substance phosphorus or nitrogen and phosphorus, such that the COD, Kjeldahl nitrogen, and total phosphorus is 200 to 500:5:1, where the nitrogen-containing nutrient substance is urea, ammonium hydrogen carbonate or ammonium sulfate, phosphorus-containing nutrient substance is monopotassium phosphate or dipotassium phosphate, and nutrient substance of nitrogen and phosphorus is selected such that Kjeldahl nitrogen content is more than 100 mg/l and total content of phosphorus is more than 20 mg/l, in the fermentation industrial waste water, and adjusting the pH of steam water washing solution by using alkaline matter to 4.5-7, so as to obtain solution; preparing liquid seed for steam water washing liquid at 15-40 degrees C, by acidifying for 2-14 days to obtain liquid seed; adding prepared mixed solution to the liquid seed and solvent according to volume ratio of 1:1-19 to obtain the mixed solution; and performing acidification reaction to mixing solution at 15-40 degrees C, by standing acidification or continuously acidifying reaction, where acidification time is 2 hours, and acidifying mixing of the solution is 25%, so that the mixed solution can be used for anaerobic fermentation of mixed solution to produce marsh gas. The fermented industrial waste water is white distillery yeast waste liquid having Kjeldahl nitrogen content of more than 100 mg/l and total content of phosphorus of more than 20 mg/l. The acid mixed solution is the liquid seed in the step of adding prepared mixed solution to the liquid seed and solvent. The steam-exploded material water washing water has COD after marsh gas production, by using tap water or acid mixing liquid, is less than 1300 mg/l of waste water. The alkaline matter is industrial liquid alkali used in an amount of (more than 30%), sodium carbonate, industrial mass fraction comprising sodium hydroxide, or lime milk (8 mass%). The method involves stewing that refers to acidizing the material solution still acidifying the acid or acid tank. The method involves continuous acidifying the acid or acid tank, adding liquid seed, adding the material liquid continuously to acid or acid tank, and the acidification reaction is in the flow of mixed liquor.