This paper focus on the flowing three parts: First introduce the high sampling rate and ultra-low frequency seismic electromagnetic field observation system. Then introduce an event adjudging and extracting approach called pretreatment of highly normalizing by discussing the advantages and disadvantages about threshold approach and short-long cycle approach. At last analyze the observation data from Huailai Station.

Results show that the method of pretreatment of highly normalizing can hardly be affected by the amplitude change of observation signal and the influence of background noise, which is a promising event extraction method in the future ultra-low frequency seismic electromagnetic field.