Abstract: According to the data collected, characteristics and index relation of electromagnetic precursory anomaly of earthquakes are analyzed. By Statistics, in general, for M≥ 3.0 earthquakes, the average time of the anomaly appearing beforehand is from ten to forty-five days. And the average distance of the anomaly transition is from 100 to 600km. The bigger the earthquake magnitude is, the earlier the anomaly appears and the longer the anomaly transmits. The probability of earthquake occurrence within two months after the anomaly appears is 93.5%. The probability of the earthquake occurrence the day or after the anomaly is over is 88% and 98% for earthquakes occurrence within 20 days after the anomaly is over.

Key words: Earthquake electromagnetic observation, Anomaly characteristics, Anomaly index relation