The invention relates to a green energy-saving prefabricated building and a construction method, comprising a base and a base plate assembly, a vertical wall panel is provided on the side edge of the upper surface of the base plate assembly, and a frame assembly is provided on the top of the vertical wall panel, The frame assembly includes crossbeams and vertical beams that are vertically fixedly connected to each other, and a shielding assembly is provided on the plane where the frame assembly is located, and the shielding assembly includes a transparent waterproof layer and a transparent radiation-proof layer sequentially arranged from outside to inside And a light adjusting device, the light adjusting device includes a plurality of uniformly arranged rotating parts. In the present invention, a shading assembly is provided on the frame main body, wherein the shading assembly includes a transparent waterproof layer, a transparent anti-radiation layer, and a light adjustment device arranged sequentially from outside to inside, and the light adjustment device includes a plurality of uniformly arranged rotating parts, In practical applications, the amount of incoming light is controlled by adjusting the rotation orientation of the rotating member, so as to achieve the effect of adjusting the intensity of indoor light.