According to the problem that the precision of time transfer over long -distance fiber based on synchronous digital hierarchy (SDH) optical network is not high and it is diffic ult to adapt to present SDH optical network,a new technique of two-way time transfer with passive listening and extending transfe r distance based on SDH optical network has been proposed.Basic principle of the bridged technique of e xtending transfer distance has been given.The errors brought by the measurement of bridg ed equipments and comparison of frame header have been analyzed.The experiment on 220km optical f iber including 4SDH equipments in the laboratory has been realized.By using bridge techniques,two SDH equipments are went across.Meanwhile,the time delay data from bridged equipments has been used for servo control every second.Therefore the clock at remote station keeps tracking the clock at source sta- tion.The peak-to-peak value of synchronization error of this system is 965 ps.The rms- difference is 117.7ps.The results of experiment show that the bridge and servo technology is useful for ex tending transfer distance.It is a feasible way for regenerating highly synchronized time at remote station.Also ,the precision of time transfer has reached a high level in the experiment.