Time synchronization techniques, especially on the pulse per second (PPS) temporal basis, have attracted growing research interests in recent years. In this paper, we have proposed and experimentally demonstrated a high-precision two-way time transfer (TWTT) system to realize long-distance dissemination of 1 PPS signal generated by a hydrogen maser. A dense-wavelength-division-multiplexing (DWDM) system and bi-directional erbium-doped fiber amplifiers (Bi-EDFAs) have also been adopted to suppress the impact of Rayleigh backscattering and optimize the signal to noise ratio (SNR) as well. We have theoretically analyzed the systematic delay in detail. The ultimate root mean square (RMS) variation of time synchronization accuracy is sub-26 ps and the time deviation can be reduced to as low as 1.2 ps at 100 s and 0.253 ps at 12 000 s, respectively.