With the introduction of wireless channel-based distribution differential protection into the distribution network, one of the key techniques to be developed is the synchronization of fault data at both ends. The method of synchronization based on the voltage surge at the time of protection activation can achieve data synchronization without adding additional equipment. However, there is a lack of the necessary theoretical analysis and verification of the synchronization accuracy and applicability of this method. In the paper, the synchronization principle of differential protection based on voltage mutation under multiphase fault conditions is studied using the superposition principle. The effects of different fault initiation threshold, sampling frequency, fault initial angle, harmonics and sampling moment of each side device on the synchronization error are further analyzed. A simulation test is carried out through ATP modeling, and the results show that taking 5% of the voltage rating as the starting threshold and using 240 sampling points per wave can ensure that the starting synchronization error of each side device is less than 30°, thus satisfying the synchronization requirement of distribution network differential protection. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. 52094020000Y).