The fifth generation mobile communication system (short for 5G) is an extension of the 4G system with the fifth generation mobile communication technology. Ultra-high precision time synchronization is one of the key technologies in 5G network. It needs to synchronize the fronthaul, midhaul and backhaul devices with ultra-high precision. As with current time server and performance of 4G supporting network it is not more able to meet the new requirements in 5G network, China Mobile, the leading operator in China, is positively striving to put forward the requirements and schemes for ultra-high precision time synchronization performance with ±50ns accuracy in time server, ±200ns in transmission network, and ±50ns in base station.