Abstract: UM-BUS is a high-speed serial bus oriented to embedded systems, the variable time slot rotation method is adopted to support multi-master working mode, which can detect faults in real time and has dynamic fault tolerance. In order to improve the time certainty of the bus system in embedded applications and ensure the accuracy of the time slot rotation of the bus node.This paper designs a high-precision time synchronization method that can correct line transmission errors and supports active fault tolerance for time master node failures. In an actual system with a bus operating rate of 1.6Gbps, the node synchronization time error is less than 50ns, and the time slot count error is less than 1 bus bit.