This paper introduces electromagnetic wave anomalies before some earthquakes observed at some observing points in Zhangye region, Gansu Province. These anomalies generally appeared a few hours, some days to more than ten days before earthquakes. The signals of electro-magnetic wave anomalies are low-frequency disturbances or continuous bidirectional strong pulses with higher frequency. The results observed show that electromagnetic wave anomaly can be regarded as a shortterm and imminent predicting index of earthquake.