NOVELTY - Preparing fertilizer by comprehensive utilization of fresh oil slag involves: adding fresh oil slag into container, adding water and lipase, reacting at 35-45 degrees C for 40-50 hours to form lipase oil solution, boiling obtained lipase oil solution for 10-15 minutes, cooling, adding neutral protease, and then reacting at 50-60 degrees C for 2-3 hours to obtain oil hydrolysates, filtering and separating out liquid enzymatic hydrolysates and solid enzymatic hydrolysates; and preparing foliar fertilizer and granular organic fertilizer by using liquid and solid enzymatic hydrolysates.    USE - For preparing fertilizer by comprehensive utilization of fresh oil slag (claimed).    ADVANTAGE - The present method prepares fertilizer with good yield; takes full advantage of fresh oil slag; and provides fertilizer which can increase crop yield and improve the crop quality.    DETAILED DESCRIPTION - Preparing fertilizer by comprehensive utilization of fresh oil slag involves: taking 10-20 parts fresh oil slag, adding it into container, adding 80-100 parts water, adjusting the pH value to 7.5-8.2, then adding 0.1-0.2 parts lipase, stirring for 2-5 minutes, then reacting at 35-45 degrees C for 40-50 hours, stirring once every two hours for 2-4 minutes, to obtain the lipase oil solution, taking lipase oil solution, boiling for 10-15 minutes, cooling, adjusting pH value to 6.8-7.2, then adding 0.2-0.5 parts of neutral protease, stirring for 2-5 minutes, and then reacting at 50-60 degrees C for 2-3 hours, stirring once every half hour for 1-2 minutes to obtain the oil hydrolysates, filtering the oil hydrolysates and separating out liquid enzymatic hydrolysates and solid enzymatic hydrolysates; taking 65-90 parts obtained liquid enzymatic hydrolysates, adding 10-20 parts potassium dihydrogen phosphate, 2-10 parts trace element solution and 0.2-0.8 parts preservative, uniformly mixing to obtain the foliar fertilizer; and taking obtained solid enzymatic hydrolysates and adding 30-50 parts animal excrement, 10-30 parts crop straw, and 30-50 parts stacking fermentation agent, and drying to obtain powdery organic fertilizer, or further granulating according to conventional technology to obtain granular organic fertilizer.