Abstract: Tianwen-1 Mars exploration mission is a mission for China to “Orbit, Fall and Patrol” Mars though a launch. Entry, Descent and Landing (EDL) of Mars exploration mission is a key part in the whole mission process. Based on the characteristics of relay communication task in this process, this paper introduces the relay communication system scheme and key technology of Tianwen-1 Mars probe adapted to the characteristics of complex timing, high autonomy, black barrier phenomenon and high dynamics of EDL segment communication task. At the same time, combined with the landing mission of Tianwen-1, the in orbit verification of relay communication in EDL is summarized and analyzed. The relay communication scheme proposed in this paper successfully supports the relay communication mission of the EDL section of the Mars Exploration of Tianwen-1.