The invention discloses water-based paint and a preparation method thereof. The formula of the water-based paint disclosed by the invention comprises the following ingredients in percentage by mass on the basis that the total mass percentage is 100%: 28-35% of acrylic resin, 37-45% of dyeing agent, 2-6% of alumina, 2-4% of light diffusion agent, 22-30% of ethanol, 0.8-1.6% of adjuvant and 2-6% of water. According to the water-based paint disclosed by the invention, LED (Light Emitting Diode) lamp bulbs or LED lamp tubes can achieve a very good light dispersion effect, and the light transmittance is increased and reaches up to 95%, so that the total light efficiency of products is increased; according to the preparation method, the combination of photoelectric technologies and the traditional coating industries is emphasized, so that energy sources are saved effectively; meanwhile, compared with the traditional oil-based paint, the water-based paint disclosed by the invention is more environmental-friendly and safer, is the main force for the development of LED traditional lighting in the future, and has broad application prospects.