High speed photography was used to determine the random variables of electrical detonator properties such as action time,and their synchronism was characterized with the initiation time difference (ITD) obtained therefrom.Studying the functional relation between the batch detonators’ initiation synchronism standard deviation (ISSD)and the samples’ITD shows,when the ISSD of the batch detonators is given, the ITD of samples consisting of n detonators will not exceed the stipulated probability. On the contrary,if the samples’ITD does not exceed the stipulated probability,the ISSD of batch detonator can be found out,and the measuring error is less or equal to 0.03μs.This method is valuable for both research and application of electrical detonators.