The invention relates to a precast composite outer insulated wall plate and a manufacturing method thereof. The plate body of the precast composite outer insulated wall plate is sequentially provided with a structural layer, an insulated layer and a protective layer from inside to outside, wherein a reinforcing cage is arranged in the structural layer; a reinforcing mesh is arranged in the concrete of the protective layer; the structural layer, the insulated layer and the protective layer are alternately anchored together through connecting pieces which are in point distribution; the left edges and the right edges of the protective layer and the insulated layer protrude out of the structural layer; a convex opening downwards extends from the lower edge of the protective layer; the tops of the protective layer and the insulated layer upwards protrude out of the structural layer; and the upper edge of the protective layer is provided with a concave opening corresponding to the convex opening of the adjacent precast composite outer insulated wall plate at the upper layer. The wall plate simplifies the construction processes, accelerates the construction speed and reduces the engineering cost. Moreover, products precast in factories have consistent specification and uniform quality, the construction quality of the building structure can be fully ensured, industrialization, standardization and generalization of building walls are realized, and the invention can be widely applied to construction of reinforced concrete buildings in building industry.