NOVELTY - Recovering vegetable oil from waste clay, comprises (i) extracting waste clay oil by solvent extraction method; (ii) separating extracted solvent and oil by fractionation method; (iii) carrying out esterification reaction by adding methanol/ethanol and sulfuric acid into extracted oil; (iv) carrying out transesterification reaction; (v) separating transesterified product with methyl ester/ethyl ester and glycerol, and separating lightweight methyl ester/ethyl ester; and (vi) purifying glycerol and methyl ester/ethyl ester by neutralizing, washing, separating oil-water, and distilling.    USE - The oil is useful in bio-diesel oil.    ADVANTAGE - The method utilizes waste clay which can be mixed with soybean meal for utilizing as a feed; not only reduce the costs of waste disposal, but also increases revenue; does not cause spontaneous combustion hazardous, due to less waste clay contained in oil; produces oil having high conversion rate, which meets the US biodiesel and consistent standards; and is economical.    DETAILED DESCRIPTION - Recovering vegetable oil from waste clay, comprises (i) extracting waste clay oil by subjecting vegetable oil waste clay to solvent extraction method, and desorbing, where the waste oil content is less than 2%; (ii) separating the extracted solvent and oil by fractionation method, recovering solvent and oil, and recovering the extracting solvent; (iii) adding methanol/ethanol and sulfuric acid into extracted oil, where the molar ratio of methanol/ethanol and sulfuric acid and extracted oil, is 8-9, and the weight ratio of sulfuric acid and oil is 0.01-0.02, reacting at 30-65 degrees C for 30-120 minutes, and carrying out esterification reaction of free fatty acids, so that the content of free fatty acids in the oil, is less than 2%, to obtain pre-esterified oils, and removing methanol/ethanol and water from oil by subjecting the residues to fractionation process at 105-120 degrees C, so that the moisture content of oil is 0.5% or less; (iv) carrying out transesterification reaction of oil by adding an alkaline catalyst into oil added with methanol/ethanol, where the molar ratio of methanol/ethanol and oil, is 6-12, and the weight ratio of alkaline catalyst and oil, is 0.01-0.02, transesterification reaction time is 30-90 minutes, reaction temperature is 60-80 degrees C, and the oil is converted into methyl ester/ethyl esters and glycerol; (v) allowing the mixture to stand for separating the transesterified product with methyl ester/ethyl ester and glycerol so as to allow the deposition of glycerol to the bottom due to gravity, and separating lightweight methyl ester/ethyl ester; and (vi) purifying glycerol and methyl ester/ethyl ester by neutralizing, washing with water, separating oil-water, distilling for removing residues of alkaline catalyst, methanol/ethanol and water, and adding medicine and acetic acid, where the weight ratio of acetic acid and oil, is 0.015-0.03, and the molar ratio of the amount of water used for washing and oil, is 3-9, and the distillation temperature is 105-120 degrees C.