The invention relates to a waterproof decoration heat-insulation outdoor environment-friendly composite decoration plate, which consists of a molding face materiel and a heat insulation layer compounded into a whole with the molding face materiel, wherein the molding face materiel is prepared from the following materials in parts by weight: 100 parts of magnesia, 5 to 10 parts of diatom ooze, 10 to 20 parts of pulverized fuel ash, 2 to 4 parts of 3MM glass fiber, 0.2 to 0.4 parts of trisodium phosphate, 2 to 3 parts of ferric oxide, 0.2 to 0.4 parts of defoaming agents, 20 to 30 parts of magnesium sulfate, 30 to 40 parts of magnesium chloride and 30 to 50 parts of water; the heat insulation layer is prepared from the following materials in parts by weight through mixing: 60 to 70 parts of sucrose polyether polyol with the hydroxyl value being 500, 7 to 10 parts of amino polyether polyol with the hydroxyl value being 500, 20 to 30 parts of polyether polyol with the hydroxyl value being 360, 15 to 25 parts of physical foaming agent CFC-141B, 3 to 6 parts of water, 1 to 2 parts of cyclohexylamine, 0.3 to 0.5 parts of pentamethyl-diethylenetriamine, 3 to 5 parts of silicone oil, 20 to 30 parts of expansion graphite and 120 to 150 parts of coarse MDI. The composite decoration plate and a manufacturing method of the composite decoration plate have the advantages that by aiming at the vacancy of the existing market product or the limitation of the user perform, through the material formula development and the production processing mode improvement, the environment-friendly, fireproof and waterproof effects are really achieved; the heat function is realized; the appearance is exquisite; the color is lifelike; the installation is simple; the composite decoration plate can be used outdoors for a long time.