Abstract: The paper develops a methodology for analyzing the compatibility of International Mobile Telecommunications 2020 (IMT-2020) and inter-satellite services (ISS) in the 26 GHz band, based on relevant ITU recommendations and reports, and current technical characteristics of both systems. It is proposed to model the massive IMT-2020 (5G) base stations around the world into a set of central base stations, and to analyze the temporal and spatial characteristics of interference from 5G base stations to ISS. Based on the IMT-2020 (5G) base stations in mainland China, the spatial characteristics of the interference to ISS are analyzed. The actual population is also taken into account in the calculation of aggregate interference of IMT-2020. The results show that these two systems have considerable possibilities in coexistence in the 26 GHz frequency band.