Abstract: The anomalies of earth resistivity in the joint area of Shanxi, Hebei and Inner Mongolia region before some medium and strong earthquakes have the following characteristics:(1) the occurrence time of resistivity anomaly is short and its amplitude is small in the epicenter region before a earthquake;(2) the anomalies before some medium and strong aftershocks after the main shock are clear, with large amplitude and lasting at low value or yearly annual variation disappearing, (3) Anomalies occurred early in marginal area with obviously anomaly form and long tendency turning.Based upon comprehensive analysis to the anomaly features in this area, and using the method of monthly speed introduced from the softweare in the ninth five years breakthrough project, we analyzed this kind anomalies effectively, and present a set sethod for analysis and prediction suitable to the area.