Biodiesel additive and preparation method thereof

The invention relates to a biodiesel additive and a preparation method thereof. The additive comprises, by weight, 60-70 parts of C9-18 alkane, 8-12 parts of ferment, 6-7 parts of a stabilizer, 2-5 parts of a dispersant, 0.1-0.3 parts of N,N'-bis(salicylidene)propanediamine and 14-22 parts of a solvent. The preparation method comprises the following steps: weighing above raw materials according to above weight parts, sequentially adding the raw materials into a reaction kettle, heating, and uniformly stirring for 20min when the raw materials are heated to 30-40DEG C to obtain the biodiesel additive. The biodiesel additive can clean carbon formed on a diesel engine to maintain an oil way unblocked in order to improve the combustion performance and the economy performance of the diesel engine. The biodiesel additive has the advantages of good combustion supporting and smoke eliminating effects, great reduction of the tail emission of the diesel engine, environmental protection and energy saving.