The invention discloses a nano fuel additive. The nano fuel additive is prepared from, by weight, 20-30% of nano cerium oxide, 4-6% of submicron copper powder, 10-20% of methyl alcohol, 10-15% of acetylacetone, 10-15% of polyglycol ether, 10-15% of polyethylene glycol and 10-15% of glycerol. A preparing method for the nano fuel additive includes the steps that nano cerium oxide, submicron copper powder, methyl alcohol, acetylacetone, polyglycol ether and polyethylene glycol are added into a reaction kettle by a ratio, heated to 70 DEG C-90 DEG C, and stirred for 5-6 h to be mixed uniformly, heating is stopped, when the mixture is cooled to 40 DEG C-60 DEG C, glycerol is added and stirred uniformly, and the nano fuel additive is obtained through cooling. The nano fuel additive has the simple components, is low in cost, improves the combustion efficiency of fuel, reduces emission of harmful substances in the combustion process of the fuel, achieves dispersity of nano particles in the fuel and improves the own lubricating performance of the fuel.