There are difficulties of fault location and reliability deficiency in existing communication channels in power systems. This paper discusses the feasibility of using 5G communications in relay protection from the aspects of message format, bandwidth demand, transmission delay, communication architecture, security and the synchronization of data based on the communication performance requirements of relay protection. It suggests that pilot protection based on 5G communication can fully make use of its advantages when it is used in distribution power systems, while the network structure and forward protocol should be optimized when it is used in medium and high voltage power systems. Finally, for the error code, frame loss, communication interruption, abnormal transmission delay, abnormal time service and other abnormalities, corresponding protection strategies are proposed. These provide an engineering application of 5G communication technology in the field of power system relay protection. This work is supported by the Science and Technology of the Headquarters of State Grid Corporation of China (No. 5700-202019174A-0-0-00) and the Project of State Grid Zhejiang Electric Power Co., Ltd. (No. 5211JX18013W).