The invention provides a building external facade assembly structure and a building external fa ade forming process. The building external facade assembly structure comprises two elastic lining platebodies, biomimetic material decorative surface layers are bonded to one sides of the elastic lining plate bodies, and the elastic lining plate bodies are bonded to each other and arranged on a rope ina sleeve mode through the biomimetic material decorative surface layers. According to the structure and the process, by arranging a PVC plate, the structure can be suitable for arc-shaped surface design of a building, smooth streamline is guaranteed, after a biological woven material layer is bonded to the PVC plate through a PVC adhesive, the whole structural strength is enhanced, the biologicalwoven material layer is not prone to breakage in the air, even if part of the biological woven material layer is broken, the biological woven material layer is attached to the PVC plate bodies through the adhesive, and the situation that the biological woven material layer flutters along with wind is avoided, so that the building attractiveness is improved, before the external facade is erected,the assembly structure of the preset face can be assembled in a workshop in advance, only the assembly structure needs to be installed on the rope on site, efficiency is high, and the high-altitude operation time of workers is shortened.