Biodiesel is receiving increased attention as an alternative, non-toxic, biodegradable and renewable diesel fuel and contributes a minimum amount of net greenhouse gases, such as CO2, SO2 and NO emissions to the atmosphere. Exploring new energy resources, such as biofuel is of growing importance in recent years. The possibility of obtaining oil from plant resources has created a great importance in several countries. Vegetable oil after esterification being used as bio diesel, Considering the cost and demand of the edible oil is bearable, so it may be preferred for the preparation of bio diesel in India. The transesterification of waste cooking oils with methanol as well as the main uses of the fatty acid methyl esters are reviewed. The general aspects of this process and the applicability of different types of catalysts (acids, alkaline metal hydroxides, alkoxides and carbonates, enzymes and non-ionic bases, such as amines, amides, and guanidine and triamino (imino) phosphoranes) are described. Transesterification is carried in a reaction cavity, once the reaction is complete, glycerine and biodiesel are gravity separated.