At present, fault recorders (FR) of multi-substation are connected to a network. After a fault occurs, due to the time unsynchronized FR which use impulse signal as time synchronization method, it is hard to associate different FR data contributed by different FR from different substations at the same time, especially, several faults happened on power grid in a short time. To solve this problem, by detecting time differences of different FR located in different substations through software method, fault data from FR of multi-substations is automatically associated. Furthermore, a synchronization method for multi-substation FR data, which does not utilize the parameters of transmission lines, is put forward to synchronize the associated data. This method is implemented in a FR network system by using software, which proved that it is a real-time, more convenient and accurate method for fault analysis of power grid.