NOVELTY - Biodiesel oil is prepared from waste by precipitating waste material at 80-100 degrees C for 2 hours, collecting supernatant, filtering by using multilayer gauze as filtering mesh to remove fine particle impurities, adding 5-10 mass% active carbon to oil, stirring for 12 hours, allowing to stand for 10-12 hours, filtering active carbon, adding proper amount of zeolite or ceramic piece at 85-95 degrees C, drying in vacuum for 2-10 hours, adding sulfuric acid and methanol, and stirring at 60-70 degrees C for 3-7 hours, wherein mole ratio of methanol and oil is 15:1-25:1 and amount of sulfuric acid is 3-5 wt.%.    USE - Preparation of biodiesel oil from waste (claimed).    ADVANTAGE - Preparation of biodiesel oil is simple and environmentally friendly, and product yield is high.    DETAILED DESCRIPTION - Biodiesel oil is prepared from waste by precipitating waste material at 80-100 degrees C for 2 hours, collecting supernatant I, filtering by using multilayer gauze as filtering mesh to remove fine particle impurities, adding 5-10 mass% active carbon to oil, stirring for 12 hours, allowing to stand for 10-12 hours, filtering active carbon, adding proper amount of zeolite or ceramic piece at 85-95 degrees C, drying in vacuum for 2-10 hours, adding sulfuric acid and methanol, stirring at 60-70 degrees C for 3-7 hours, wherein mole ratio of methanol and oil is 15:1-25:1 and amount of sulfuric acid is 3-5 wt.%, washing with methanol, washing with water, adding proper amount of zeolite or ceramic piece at 85-95 degrees C, drying in vacuum for 2-10 hours, adding potassium hydroxide (KOH) and methanol, stirring at 60-70 degrees C for 0.5-2 hours, wherein mole ratio of methanol and oil is 15:1-25:1 and amount of KOH is 0.15-0.3 wt.%, washing with methanol, washing with water, adding zeolite or ceramic piece at 85-95 degrees C, drying in vacuum for 2-10 hours, and measuring acid value of product to determine if biological diesel oil reaction is not complete and if acid value of oil is greater than or equal to 0.8mg KOH/g.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow diagram of the preparation of biodiesel oil. (Drawing includes non-English language text).