Abstract: As one of the important means for earthquake precursor observation, electro-magnetic disturbance observation has drawn considerable attention of seismologists both at home and abroad. When no electro-magnetic events occurred, observation instruments could only record chaotic electro-magnetic field, so we could not confirm whether the instruments were working properly or not. For this reason, we developed an inspection equipment in accordance with the electro-magnetic disturbance observation standard enacted by China Earthquake Administration, and applied it at stations successfully. The inspection instrument is started each month to check regularly the electro-magnetic disturbance observation system, providing technical support for the identification of anomalous events.