The differential protection of power system puts forward higher requirements on the real-time data transmission for double terminals' information. Larger transmission delay is likely to influence the synchronization precision and cause the refusing act and incorrect operation of relay protection. So the channel delay problem must be given full consideration to protect in practical application. But the delay effect caused by electrical measurement cannot be ignored in UHV long-distance transmission system, the traditional method of delay analysis without considering the effect of electric parameters as traveling wave. This paper considers the process from the failure happening to the protection completing fault diagnosis, and the delay of electric parameters traveling wave and the optical signals in each link. Different fault location and communication equipment lead to uncertainty of channel delay, then through three kinds of random distribution of delay model are used to reflect the differences in total delay and the results are compared and analyzed. The result shows that normal distribution is more suitable for delay distribution, research conclusion can be applied in optimal selection of protective devices and data synchronization on both sides. Finally, the relationship between the delay of communication and the network nodes is analyzed by using the normal distribution.