The invention discloses a high-strength fireproof building composite heat-insulated board and a preparation method thereof. The high-strength fireproof building composite heat-insulated board is prepared by the raw materials by weight ratio: 35-45 parts of Portland cement, 14-25 parts of bamboo charcoal, 6-11 parts of perlite, 9-22 parts of sea-foam stone powder, 15-25 parts of organic silicon-modified epoxy resin, 10-19 parts of gypsum, 14-27 parts of pyrophyllite, 5-11 parts of inorganic fiber, 12-22 parts of foam glass, 1-8 parts of palygorskite, 2-6 parts of scolecite, 9-15 parts of acrylate, 1-7 parts of quartz sand, 2-6 parts of attapulgite, 3-12 parts of polymer emulsion, 2-4 parts of surfactant, 2-6 parts of waterproof agent, 2-5 parts of modified additive, 1-3 parts of defoaming agent and 2-15 parts of water. The high-strength fireproof building composite heat-insulated board, which is prepared from the raw materials of the Portland cement, the bamboo charcoal, the perlite, the sea-foam stone powder, the organic silicon-modified epoxy resin, the gypsum, the pyrophyllite, the inorganic fiber, the foam glass, the palygorskite, the scolecite, the acrylate and the quartz sand according to an effective mixing ratio, has the advantages of high compressive strength, heat insulation, good fireproof performance, corrosion resistance, moisture resistance and so on.