IEEE 1588v2 protocol is mainly used in carrier level ground time service, which can meet the requirements in 4G phase, but can not meet the requirements of some applications of 5G communication. In order to further improve the accuracy, this paper uses time synchronization technology based on white rabbit precision time protocol(WR-PTP) to achieve sub nanosecond synchronization. In this paper, after deeply studying the technical characteristics of WR-PTP, the WR-PTP clock module with long-distance transmission capability is developed based on WRPC-v4.2 kernel. By correcting the asymmetry of the transmission link, an experiment was carried out on a 100 km long-distance point-to-point optical fiber link. The measured time synchronization deviation was 41.5 ps and the time synchronization accuracy was -9.5 ps.