This book focuses on the theories and techniques for LEO Satellite Internet of Things, which provides a systematic and in-depth exploration of the architecture, key technologies, and integrated applications of Low Earth Orbit satellite-based IoT networks. It covers crucial topics such as constellation design, channel acquisition, multiple access, robust transmission, and inter-satellite cooperation, with a strong emphasis on modeling, optimization, and deep learning-assisted methods. It features extensive simulation results, illustrative figures, and clear structural presentations, offering readers both theoretical foundations and practical insights. It will benefit researchers, engineers, and students by providing comprehensive knowledge and design methodologies for next-generation space-air-ground-sea integrated communication systems.