The invention relates to a production method of a composite board and particularly relates to a production method of a fireproof composite board. The method comprises the following steps: producing a core layer, mixing a raw material of the core layer, then thermally pressing and shaping, then successively coating the raw material of the core layer with hot melt adhesive and a fireproof layer from top to bottom, putting the raw material of the core layer in a thermal rolling machine, and curing to obtain a finished product. Compared with the prior art, the production method of the fireproof composite board has the advantages that the fireproof composite board produced by the method is overall non-combustible, can tolerate high temperature of 1000 DEG C, can reach fireproof class A1, is non-combustible, is high in strength and is environment-friendly, the density of the fireproof composite board is not higher than 1.6g/cm<3>, the service life is 30 years or longer, the fireproof composite board is free of rust, free of mildew and free of returned halogen in a using process, and the fireproof composite board is wide in application range and can be applied to constitution structures and fireproof parts of houses, commercial buildings, aircrafts and water carriage.