The invention aims to provide an alumina electric furnace cover, which is high in thermal shock resistance, density and iron slag erosion resistance and long in service life. The alumina electric furnace cover comprises the following components in percentage by weight: 5 to 20 percent of 88 homogenized alumina particles, 8 to 35 percent of electrofused low-carbon brown aluminum oxide particles, 10 to 25 percent of electrofused mullite particles, 10 to 15 percent of andalusite particles, 10 to 15 percent of electrofused white corundum fine powder, 3 to 5 percent of alpha-Al2O3 micro powder, 2.5 to 7 percent of calcium aluminate cement, 1 to 2 percent of explosion-proof fibers, 2 to 4 percent of reinforced heat-resistant steel fibers, 2 to 4 percent of silicon dioxide micro powder and 2 to 5 percent of chromium oxide. A preparation method comprises the following steps of uniformly mixing the electrofused white corundum fine powder, the alpha-Al2O3 micro powder, the silicon dioxide micro powder and the explosion-proof fibers; adding the electrofused mullite particles and the andalusite particles, stirring the mixture for at least 3min, adding the other raw materials, and stirring the mixture for at least 8min; adding water and a water reducing agent, performing stirring and casting molding, and performing natural curing, de-molding and drying.