Abstract: Terahertz (THz) band, as the ultra-high communication band which has not yet been fully developed, has large bandwidth and other advantages.Its application in the 5th generation (5G) and Beyond 5G (B5G) systems can achieve higher transmission speed and realize the sharing of terrestrial mobile networks and satellite network spectrum resources, which is conducive to promoting the construction of a new generation of air and space integrated communication network.In this paper, a THz channel modeling and simulation schemeis proposed for the satellite-ground communication system. The factors which have impact on the THz channels are analyzed, including free space loss, molecular absorption loss, cloud attenuation, rain attenuation, and Doppler frequency shift. The modeling procedureis built for the satellite-ground THz communication channel and the method of generating channel parameters are presented in steps. The influence of the transmission distance and frequency on the transmission signal in different weather conditions is analyzed by numerical simulations. The bit error rate are evaluated based on the generated channel responses.Thus, the feasibility of the proposed model and method has been verified. The proposed modeling scheme can provide dynamic THz channel response data under different transmission conditions.It can provide basis for the design and development of the future THz band wireless communication systems.