The invention discloses a high-load lightweight composite ceiling, which comprises a ceiling body, a base cloth layer, a bonding layer and a fabric layer, wherein the base cloth layer, the bonding layer and the fabric layer are sequentially arranged from bottom to top; the bonding layer comprises a honeycomb paperboard layer and foaming resin and glass fiber blend layers attached to two side surfaces of the honeycomb paperboard layer. The invention further relates to a molding device and molding method of the high-load lightweight composite ceiling. The high-load lightweight composite ceiling has the technical effect that a glass fiber spray machine and a spray gun are arranged and the foaming resin and glass fiber blend layers cover the two side surfaces of the honeycomb paperboard layer, so that the composite ceiling is light in weight and high in bearing strength.