The problem that the internal electrical interference is nuavoidable for differential coil in measuring fast high current impulse is discussed.The shielded differential coil which has a chink in the middle of its shield can reduce this interference,and that the signal to noise ratio of the differential measurement is 27 shows the anti interference efficiency of this coil.Furthermore,the double differential coil which use the differential balanced technique to resisting the interference make the signal to noise ratio of the differential mearsurement be 57.