IEEE 1588 protocol provides a high-precision network synchronization mode and it has significant value in network communication of smart substation. An IEEE 1588 clock mode is analyzed that is more suitable for smart substations based on the capability of anti-network traffic

timestamp accuracy and reliability. Considering the characteristics of the network packets in the process layer and the actual conditions

the influence of the traffic-filtering function by IEEE 1588 switch and its shortcomings on the performance of IEEE 1588 synchronization are analyzed. A hardware clock functional test platform in process level “three-in-one” mode is built to test the impact of background flow on the IEEE 1588 synchronization with normal or invalid virtual local area network(VLAN). The influence of synchronous deviation of IEEE 1588 on the measurement errors of phasor measurement unit(PMU)under the switch traffic is finally analyzed by simulation.