The invention discloses a modified polyurethane thermal-insulation composite board. The composite board sequentially comprises a gypsum board layer, a thermal-insulation board layer and a cement board layer from inside to outside, wherein the thermal-insulation board layer is prepared from modified polyurethane, acrylate, diisocyanate, an alkyd resin, dipropylene glycol monobutyl ether, an organic silicon resin, a melamine formaldehyde resin, chlorinated paraffin, diisocyanate, nitrocellulose, glass fibers, nano calcium carbonate, perlite, fly ash, magnesium oxide, n-octanol, lauryl alcohol, hexadecanol, polymer dibasic alcohol, fluorine-containing polyether dibasic alcohol, a compatilizer, an emulsifier, a foaming agent, a silane coupling agent, a curing agent and silicone oil. The modified polyurethane thermal-insulation composite board has excellent thermal insulation property and excellent heat resistance.