Railways are the economic artery of the nation, a major livelihood project and the backbone of the comprehensive transport system, and an important national industry of a fundamental, service and pillar nature. The integration of railway development with the new digital infrastructure is not only a requirement of the new era, but also an urgent need for railways to improve efficiency and effectiveness and maintain high quality development. Most of the research conducted on 5G technology in railways at home and abroad has been limited to the adaptation and service application of 5G technology in railways, focusing on the improvement of existing railway service applications and the expansion of new services and needs brought about by the technical advantages of large bandwidth and low latency brought about by 5G, with less research conducted on the network service quality and detection architecture of 5G in railway applications. This paper firstly reviews the current status of railway 5G research and the progress of application trials at home and abroad. It then introduces the main key technologies and the 5G networking architecture defined by 3GPP to support 5G with large bandwidth, low latency and massive connectivity. By studying the key network technologies and 5G-R network architecture, it provides a theoretical basis for future research on the architecture of the testing system, testing methods and proposed testing metrics.