According to electromagnetic disturbance (EMD) data based on AETA, a multi-component seismic monitoring and prediction system, this paper conducts features analysis, anomalies identification and correlation analysis combining with seismicity. The result shows that EMD data are different with environmental noise and human noise. It might be generated by the change and movement of free charge near the surface according to the principle of magnetic sensor and the derivation of Maxwell’s equations. Take Jiuzhaigou Ms 7.0 earthquake and Changning Ms 6.0 earthquake in Yibin as examples, a determined connection between EMD anomalies and earthquake was found. Periodic SRSS and ultra-low frequency EMD along the relerant bands of the Longmenshan fault and Xianshuihe fault zones might imply a risk of strong earthquake. We also discuss the physical mechanism of the EMD source and suggest that it may be related to the overflow of charged particles from the molten mantle into the crust. Under movement of earth rotation and revolution, the daily periodic fluctuation of the sunrise and sunset will occur in a specific related latitude and longitude region or area close to epicenter.