The invention relates to a concrete heat preservation composite component plate, an outer wall building envelope and an assembling method. The component plate is provided with latticed concrete rib frameworks, the concrete rib frameworks are internally provided with rebar inner net racks, the space between the concrete rib frameworks and the exterior of the concrete rib frameworks are filled with heat preservation material layers, the outer surfaces of the heat preservation material layers are wrapped with concrete layers, the concrete layers are internally provided with rebar outer net racks, and the rebar inner net racks and the rebar outer net racks are fixedly connected through connecting pieces. The invention further provides the outer wall building envelope composed of the component plates and the assembling method of the outer wall building envelope. The concrete heat preservation composite component plate which is high in building energy saving efficiency, low in manufacturing cost, low in weight, convenient to install, long in service life, good in fireproof performance and good in outer wall combination performance, the outer wall building envelope composed of the concrete heat preservation composite component plate and the assembling method of the outer wall building envelope are provided.