NOVELTY - Preparing organic/inorganic mixed fertilizer comprises: heat evaporation of molasses fermented waste liquid and cooling the liquid; alkaline hydrolysis dehydration of a part of obtained liquid concentrate and alkaline hydrolysis agent, and then adding calcium magnesium phosphate fertilizer, and potash fertilizer; acid dehydration of part of obtained liquid concentrate and acid hydrolysis agent; mixing the obtained acid-base demodulation material and seasoning; drying the material; performing biological fermentation; and adjusting pH of the active organic fertilizer.    USE - The method is useful for preparing organic/inorganic mixed fertilizer (claimed).    ADVANTAGE - The modern method combinedly uses acidification and basification process for rapidly fermenting molasses waste liquid concentrate without adding additional acid and alkali for neutralizing purpose.    DETAILED DESCRIPTION - Preparing organic/inorganic mixed fertilizer comprises: (1) heat evaporation of molasses fermented waste liquid having organic material content of 40-75% to obtain a concentrated liquid, cooling the concentrated liquid and dividing the liquid into two parts, where one part is used for alkaline hydrolysis dehydration and the another part is used for acid hydrolysis; (2) performing alkaline hydrolysis dehydration by taking a part of the obtained liquid concentrate, then adding 10-35% of alkaline hydrolysis agent, stirring the mixture under alkaline hydrolysis condition for 20-40 minutes, and then adding 5-15% of calcium magnesium phosphate fertilizer, and 10-15% of potash fertilizer and uniformly stirring to obtain a demodulation base material; (3) performing acid dehydration by taking a part of the obtained liquid concentrate, then adding 10-35% of acid hydrolysis agent under stirring for 20-40 minutes to obtain a demodulation acid material; (4) uniformly mixing the obtained acid-base demodulation material, seasoning the demodulated material and adjusting the pH of the seasoned material to 5-7; (5) drying the seasoned material under ventilation condition at 35-50 degrees C until the moisture content is less than or equal to 10%; (6) performing first level biological fermentation of 15-30 pts. wt. cane slag, 50-70 pts. wt. filter mud, 10-30 pts. wt. obtained seasoned material and 2-5 pts. wt. base culture medium in an aeration fermentation stir device for 10-15 days and stirring the mixture for 1-2 times to obtain a first-stage fermentation fertilizer; (7) performing second level biological fermentation by adding 2-5 pts. wt. trace elements, and 5-15 pts. wt. probiotic seed liquid to the first-stage fermentation fertilizer, uniformly stirring the mixture for 7-10 days to obtain an active organic fertilizer; and (8) adding alkali or acid agent to the active organic fertilizer, uniformly stirring the sample to adjust pH of 5.5-7, stop adding the alkali or acid agent and drying at 40-60 degrees C under ventilation condition until the moisture content is less than or equal to 10%.