In October 2018, IEEE released the latest WiFi standard protocol 802.11ax(WiFi6). It can support both 2.4 GHz and 5 GHz frequency bands with the maximum transmission rate of 9.6 Gbit/s. At present, WiFi6 has been applied in smart home, radio, and mine construction. However, it is scarcely applied in the field of rail transit. An integrated urban train ground communication system based on WiFi6 is proposed. Aiming to the serious competition for frequency resources between production businesses, the first actual subway line test of the WiFi6 system in the country is conducted on the Dalian Metro Jinpu Line. The entire test process completely replicates the actual running scene of the train, including real vehicles, equipment, and actual communication scenarios such as elevated and tunnels. Extensive test results show that the designed WiFi6 system bears the characteristics of large network throughput, fast communication and transmission rate, long battery life, and strong AP signal coverage, satisfying the rail transit business. It can guarantee the reliable transmission of Communication-Based Train Control(CBTC) traffic and provide an efficient transmission path for Closed Circuit Television(CCTV) and Passenger Information System(PIS) traffic.