The invention discloses a die casting aluminium alloy water-based release agent and a preparation method thereof, and relates to release agents and preparation methods thereof. The preparation methodcomprises the steps that engine oil, beewax, organic molybdenum compounds and silicone oil are placed in a water bath kettle to be mixed and heated to be 50 DEG C to 80 DEG C, the materials are stirred with an electric stirring machine, polyoxyethylene aliphatate and polyoxyethylene oleyl ether are slowly added after uniform stirring, hot water is added while stirring, and the materials are emulsified into an emulsion, wherein hot water is tap water or purified water, and the heating temperature is 50 DEG C to 80 DEG C; when the emulsion is cooled to the room temperature, silicon dioxide is added while stirring, and then, stearic acid, ethyl alcohol, triethanolamine, an organosilicone wetting agent, sodium benzoate, sodium phosphate, a thickening agent, sodium nitrite and sorbic acid are added. The release agent prepared through the preparation method contains ultrafine silicon dioxide, silicone oil, and the like, heat resistance is excellent, the surface of a casting is smooth, mold sticking, strain damage or deformation defects are effectively prevented, the lubricating property of the water-based release agent is remarkably improved through lubricating oil, beewax, the organic molybdenum compounds, and the like, and the demolding property is remarkably improved.