The invention discloses a preparation method for an enamel coating on an aluminum alloy surface. The preparation method comprises the following operating steps of 1, conducting dirt removal, degreasing and surface oxidation film removal treatment on an aluminum alloy base body, then putting the aluminum alloy base body in a vacuum chamber, raising the temperature inside the vacuum chamber to 120-140 DEG C, introducing monosilane gas into the vacuum chamber after preheating is conducted for one hour, continuing to raise the temperature inside the vacuum chamber to 340-360 DEG C, stopping heating after temperature raising is maintained for 5-6 hours, and taking the aluminum alloy base body out when the interior of the vacuum chamber is naturally cooled to 90-100 DEG C; and 2, immediately spraying glaze slip with the thickness ranging from 50 microns to 70 microns to the surface of the aluminum alloy base body, putting the aluminum alloy base body into a drying oven with the temperature being 80 DEG C, putting the aluminum alloy base body into a resistance furnace after baking is conducted for 40 minutes, conducting sintering for 4-6 minutes at the temperature of 350-400 DEG C, and conducting cooling, so that a finished product is obtained. The enamel coating prepared through the method is excellent in abrasion resistance, corrosion resistance and mechanical impact resistance, and quality of the aluminum alloy product is greatly improved.