Abstract: In active distribution networks, distributed power sources and load points are numerous and widely distributed, and the occurrence of faults will be affected by various nodes. Different protection devices usually determine whether a fault has occurred by monitoring and analyzing parameters such as current and voltage, and isolate the fault area by taking corresponding protection actions. However, due to the complexity and dispersion of active distribution networks, there may be clock bias in the fault information obtained between different protection devices, which can lead to errors in the judgment of faults by the protection devices, thereby causing delays or errors in protection actions. Therefore, a current longitudinal differential protection method for active distribution networks based on fault information synchronization is designed and proposed. This method first analyzes the fault current characteristics of the active distribution network to determine whether differential protection is necessary. On the basis of determining the need for differential protection, in order to ensure synchronous fault information between protection devices, the clock correction method is used to synchronize the clocks of each device, achieving fault information synchronization. At the same time, the allowable margin of synchronization error is calculated and the tolerance range of the protection equipment for clock deviation is determined. Finally, based on the fault information synchronization method, a composite criterion for current differential protection is constructed to achieve active distribution network current longitudinal differential protection. The experimental results show that the proposed method for active distribution network current longitudinal differential protection has better accuracy and overall application effect.