With the development of communication technologies, 6G aims to achieve global seamless network coverage, and Low Earth Orbit (LEO) satellite internet is considered a critical technology for enabling 6G. The analysis and modeling of satellite mobile channel propagation characteristics is an essential and key technology in the research and design of satellite mobile communication systems. However, the satellite-ground link of LEO satellites exhibits significant differences from terrestrial cellular networks in terms of the severity and complexity of the losses encountered, meaning that traditional terrestrial cellular network channel models cannot be directly applied to LEO satellite networks. To address this issue, we have studied the propagation characteristics of LEO satellite channels in this chapter, including path loss, rain attenuation, atmospheric absorption, and terrestrial object loss. We also reviewed and introduced existing typical satellite-ground channel models, and the channel models based on artificial intelligence in recent years are also introduced. Additionally, we developed large-scale and small-scale models based on a novel geometric stochastic approach, and validated the accuracy of these models through comparison with standard and existing models. By adjusting the environmental parameters of the model through machine learning methods, it can be applied to various scenarios adaptively. Our work provides a comprehensive understanding of the propagation characteristics of LEO satellite satellite-ground channels and, through a novel approach, establishes a satellite-ground channel model that can serve as a reference for researchers engaged in satellite communication system studies.