Abstract: Aiming at the problem of time synchronization among underground large-space positioning base stations, the optical fiber time-frequency synchronization technology based on White Rabbit (WR) is studied. In view of the difficulty to calibrate the delay asymmetry coefficient of traditional two-wave bidirectional WR, the single-wave bidirectional WR is studied to solve the problem. For the single-wave bidirectional WR, even if the WR master and slave nodes use the same optical module, the central wavelength of the optical module is still not guaranteed to be exactly the same. Therefore, we analyze the fiber dispersion influence on WR time synchronization performance, and construct a time synchronization error model. In addition, a corresponding mitigation strategy is given. Using the self-developed WR engineering prototypes, the experimental verifications are performed in 50 km fiber link. The results show that the single-wave bi-direction WR can offer time synchronization accuracy better than 100 ps for the underground large-space positioning base stations.