Abstract: Dynamically Reconfigurable high-speed serial bus, UM-BUS is a novel high-speed serial bus for embedded systems. Targeting precious time synchronization among master nodes, this paper proposes a novel time synchronization method to meet the requirements of time precision in UM-BUS. In the proposed method, time is first broadcasted through time broadcast packets. Then, the transmission delay and time deviations via three handshakes during link self-checking and channel detection can be worked out referring to the IEEE 1588 protocol. Finally, each node can calibrate its own time according to the broadcasted time. The proposed method has been proved to meet the requirement of real-time time synchronization. The experimental results show that the synchronous precision can achieve a bias less than 100 ns.