Abstract: A newly developed differential lightning electromagnetic pulse instrument is introduced.Based on the cloud-to-ground lightning modulation experiments, the paper further adopts a kind of lightning orientation method in the case of default lightning polarity.The lightning electromagnetic pulse instrument is installed on the top of a 6-floor building to test the horizontal electric field from natural lightning on the ground.The measured flash horizontal electric field waveforms show that,it can not only suppress the common mode interference effectively,but also can be used for lightning orientation.