Based on the observed data of electromagnetic wave of recent six years at 14 stations in Hexi corridor of Gansu Province, this paper analyses the characteristics of electromagnetic wave anomalies before 11 earthquakes (Ms≥4.0) occurred recently in Gansu province and its vicinities.The results show that the anomalous signal of electromagnetic wave mainly has two kinds:low-frequency pulse and paroxysmal pulse; The time appearing anomalous signal and intensity are related to magnitudes and epicentral distances. The greater the magnitude and the nearer the epicentral distance, the earlier the time appearing anomalous signaliis and the bigger the amplitude is; The anomalous signal of shallow earthquake is stronger, and appears pulse form; For deep earthquake the signal is weak relatively, and appears low-frequency pulsation.The anomalous signal shows a process of concentrated-calm-earthquake triggering.