Abstract: Based on the agenda item 1.13 of WRC-19 and requirements for domestic compatibility analysis of the 5th generation (5G) mobile communication candidate frequency bands above 6 GHz, this paper studied the interference from International Mobile Telecommunications 2020 (IMT-2020) system to fixed satellite service (FSS) system in 27-29.5 GHz band. Based on the aggregate interference assessment, the interference from IMT-2020 (5G) base station (BS) to the up-link of FSS receiver where the geostationary orbit satellite at 59 degree, 85 degree and 113 degree longitude were comparatively studied. In addition, compatibility simulation under IMT-2020 (5G) base stations with different array configurations is also studied. Study shows that the IMT-2020 (5G) system will not cause harmful interference to fixed satellite services system in the frequency 27.5-29 GHz band, especially in the case of IMT-2020 (5G) base station with large scale antenna array. The results can provide the technology basis for future planning and actual deployment of IMT-2020 (5G) system in 27-29.5 GHz frequency band and protection of FSS.