The invention discloses a solar cell assembly backplane with a high CTI value. The solar cell assembly backplane consists of a substrate layer, a weather-proof layer coated on the surface of the substrate layer, and a bonding layer coated on the other surface of the substrate layer. The bonding layer can be prepared by adopting a double-layer coating method, and the weather-proof layer can be prepared by adopting a single-layer coating method or the double-layer coating method. By formula optimization of a double-layer coating, not only does the solar cell assembly backplane have the characteristics of high reflectivity, high bonding strength and good aging resistance, but also CTI performance of the backplane can be improved, insulation safety of the backplane is ensured, and a preparation method of the solar cell assembly backplane is simple in process and easy to operate.