The invention relates to a multifunctional energy-saving composite plate with a multi-layer cavity structure. The multifunctional energy-saving composite plate is arranged on the outer side of a wall body base body and is used for external heat preservation of an exterior wall. The multifunctional energy-saving composite plate with the multi-layer cavity structure comprises a protection layer, an air layer, a filling layer, a partition plate, a heat preservation layer, a partition plate and a decoration layer from inside to outside. The partition plates are arranged on two sides of the heat preservation layer and have good leakproofness and a heat reflection function and play a good heat-insulation role, material diffusion of the heat preservation layer can be further prevented, and the service life is prolonged. The air layer is formed by the gap between the protection layer and the filling layer and has fireproof and heat-insulation performance.