The invention belongs to the field of new materials for fire control, and relates to a novel fire-proof composite board. According to the fire-proof composite board, a high-strength magnesium calcium silicate jelling inorganic material is used as an upper plane material and a lower plane material, a magnesium calcium silicate structure composite layer is taken as a core layer, and aluminum sulfate fiber grid glass fibers or non-inflammable non-woven fabrics or plant fibers are taken as reinforcing materials, are laid outside the core layer and are formed in a hot-pressing and composite mode. The high-strength magnesium calcium silicate jelling inorganic material comprises, by weight, 20%-25% of magnesium sulfate, 15%-20% of calcium silicate, 3%-5% of wollastonite fibers, 30%-40% of magnesium oxide, 3%-5% of plant fibers, 3%-5% of aluminum sulfate fibers, 3%-5% of modifying agents, 3%-5% of bentonite, 3%-5% of foaming agents, 1%-3% of phosphoric acid and the balance water. The magnesium composite board can bear a high temperature of 1000 DEG C, the fire-proof performance reaches the A1 level, the material cannot crack or deform, the strength is high, the composite board is sound-proof and thermal-insulating, the service life of the composite board can reach more than 30 years, the composite board can be nailed and planed and is convenient to use, the defects that a traditional fire-proof board is flammable and prone to halogenide, efflorescence and deformation are thoroughly overcome, and the composite board is suitable for decoration fire-proof boards, fire-proof smoke exhaust air pipe and the like.