The invention discloses an additive for improving particle size of an aluminum-air battery product and application of the additive. The additive is prepared from nano aluminum oxide, polyethylene glycol (PEG) and low-carbon alcohol, wherein the PEG is one or a mixture of more than two of PEGs of which the polymerization degrees are 400, 600, 2000 and 4000; the low-carbon alcohol is one of or a mixture of more than two of methanol, ethanol and propanol. The additive for improving the particle size of the aluminum-air battery product has the advantages of low cost, high safety, environmental friendliness and the like; in addition, the influence on discharge performance of an aluminum-air battery is avoided; the particle size of the produced aluminum hydroxide is nanoscale; compared with a flame retardant and a large-particle-size flame retardant, the additive disclosed by the invention has the advantages of high dispersity in a polymer, high mechanical properties, high compatibility andmore excellent flame-retardant effect. The additive has important significance in reducing raw material consumption and use cost of the aluminum-air battery and realizing waste utilization.