The invention discloses a light fireproof insulation type composite panel suitable for a plant building, relating to a building material and solving the problem that an existing building panel can not simultaneously meet requirements of light weight, load bearing, fire prevention, and good insulation property. The light fireproof insulation type composite panel comprises raw materials of 20-90 parts of gypsum powder, 1-8 parts of gypsum fibers, 2-9 parts of pulverized fuel ash, 0.2-0.6 part of foaming agent, and 0.1-1.5 parts of sodium dodecyl sulfate. The light fireproof insulation type composite panel is prepared by adopting the following steps: grinding and crushing the pulverized fuel ash, mixing with the gypsum powder and the gypsum fibers and dissolving in water, controlling the temperature to be 20-40 DEG C, adding the foaming agent and stirring for 5-8 min, raising the temperature to 100-110 DEG C, adding the sodium dodecyl sulfate, continuously stirring for 5-8 min to obtain a sandwich material; and then laying between two precoats, and pressurizing and foaming to obtain the light fireproof insulation type composite panel. The light fireproof insulation type composite panel disclosed by the invention is suitable for a building shed and a factory, light in weight, high in strength, better in thermal insulation and fire prevention properties, and capable of thoroughly avoiding risks such as open fire combustion.