With the rapid development and wide application of internet of things (IoT) technology, optical equipment is being promoted to collect and store multi-scale remote sensing images, and to apply them in various fields such as industry, agriculture, and ecological and environmental protection. However, the resulting security risks have also caused widespread concern. This paper designs a remote sensing image synchronization encryption scheme based on 3D cross-coupled chaotic map and block-based cubes for multi-scale remote sensing images. First, a new 3D chaotic map is constructed by coupling the traditional single-node sinusoidal map, which provides support for building complex chaotic mappings for devices with limited resources. Second, a fractal square based on the Hilbert curve combined with chaos achieves simultaneous pixel scrambling and diffusion operations, improving multi-scale graphics encryption. Finally, a multi-type remote sensing graphics dataset is used for testing and a series of analysis experiments are performed to prove the feasibility of the algorithm.