NOVELTY - Preparing biogas fertilizer using beer production waste gas, comprises e.g. mixing dehydrated sludge, waste lees, and silica sludge, dividing material into two groups, carrying out dry-wet fermentation, carrying out low-high temperature fermentation, analyzing fermentation gas, carrying out enzymolysis to the fermented biogas fertilizer, stabilizing the remaining biogas fertilizer, detecting pH, organic carbon, organic matter, nitrogen, phosphorus and potassium, heavy metal and other trace elements, and using as e.g. organic-inorganic fertilizer raw material.    USE - The method is useful for preparing biogas fertilizer using beer production waste gas (claimed).    ADVANTAGE - The method has simple operation process, and low operation cost; does not produce secondary pollution; and is convenient to manage. The biogas fertilizer after stabilizing is directly used as fertilizer or used for research and development of organic-inorganic fertilizer, foliar fertilizer and irrigation fertilizer.    DETAILED DESCRIPTION - Preparing biogas fertilizer using beer production waste gas, comprises (i) mixing beer production discharged dehydrated sludge, waste lees, and silica sludge according to the weight ratio, measuring the material pH value, which is 5.5-6.8, dividing the material into two groups, adjusting the moisture content, where the first group moisture content is 85-95%, and the other group is 70-80%, and carrying out dry and wet fermentation, (ii) fermenting by: adding the prepared two groups of raw material into a fermentation tank and closing, introducing nitrogen, discharging the air in the tank to ensure the tank body under the sealing state for anaerobic fermentation, discharging the fermentation generated gas from the fermentation tank, intermittently stirring in the fermentation process, controlling the temperature of the two groups of fermentation tank at 23-27 degrees C and 48-52 degrees C, and carrying out low temperature and high temperature fermentation, (iii) analyzing fermentation gas by: gradually increasing gas production after fermentation, maintaining the temperature and stirring condition, monitoring the fermentation material pH value and gas components of methane and carbon dioxide content, the gas production rate is obviously reduced until gas production is not obvious, and completing the fermentation, and (iv) recovering fertilizer by: carrying out enzymolysis to the fermented biogas fertilizer after leaving the first part as a material of the next batch fermentation, stabilizing the remaining biogas fertilizer, and detecting pH value, organic carbon, organic matter, nitrogen, phosphorus and potassium, heavy metal and other trace elements, and after stabilizing, using it as organic-inorganic fertilizer, foliage fertilizer, and irrigation fertilizer raw material.