The invention discloses a nanometer compound water-based heat insulation anticorrosion paint used for metal and a preparation method thereof. The raw materials of the paint consists of the following components: tap water, watercraft acrylic resin, rustproofing pigment, reflection pigment and filler, hollow micro-beads, watercraft nanometer size, anti-settling agent, wetting and dispersing agent A,wetting and dispersing agent B, film-forming assistant, defoaming agent, flatting agent, anti-flash rustproofing agent and thickening agent. Watercraft polyacrylic emulsion is styrene-crylic acid copolymerization emulsion, pure crylic acid polymerization emulsion or organic silicon-crylic acid copolymerization emulsion. The wetting and dispersing agent A is block macromolecule copolymer, multivalence carboxylate polymer and / or synthetic macromolecule copolymer, and the wetting and dispersing agent B is anion wetting agent and / or nonionic wetting agnet. The product contains no organic solvent,heavy metal and other harmful substances, is extremely excellent in environmental conservation, integrates the functions of anticorrosion and heat insulation as a whole and is simple and convenient for construction, safe in storage and stable in performance.