The present invention discloses a thermal-insulation building 
thin layer aqueous 
coating material and a preparation method thereof, wherein the 
coating material comprises the following raw materials by weight: 16-30 parts of an acrylic 
emulsion, 10-20 parts of a filler, 20-26 parts of 
barium residue, 1-5 parts of kaolin, 5-18 parts of 
titanium dioxide 
powder, 1-4 parts of 
dodecanol lipoid, 0.1-0.2 part of 2-methyl-4-isothiazolin-4-one, 0.1-0.4 part of 2-n-octyl-4-isothiazolin-3-one, 0.1-0.4 part of BASF A10, 0.1-0.5 part of 
sodium polyacrylate, 8-15 parts of 
sodium tripolyphosphate, and 10-20 parts of water. The preparation method comprises: taking samples according to the weight part ratio, taking the filler, the 
barium residue, the kaolin, the 
titanium dioxide 
powder and the water, mixing, adding the 
sodium tripolyphosphate, stirring to achieve a uniform state, adding the acrylic 
emulsion and the 
dodecanol lipoid, stirring to achieve a uniform state, adding the remaining raw materials, and carrying out ball milling to obtain the finished product. According to the present invention, characteristics of good performance, low cost, energy saving, and emission reducing can be achieved.