Abstract: This paper analyze the characteristics of gravity variations in the observed area in North China using space-time scan method on basis of gravity data from 1992 to 2008.The shape, duration and magnitude of anomaly before earthquakes are summarized, and the earthquake prone region in the spatial variation of gravity field is presented.The results show that the variation of gravity field has no obvious regularity;a lot of sites show clear tendency anomaly;the variation of gravity field is correlative closely with the earthquakes in and around the net, and most of the anomalies occur 2 years before the earthquakes;0 gradient line, high gradient zone and extreme center of gravity field are the earthquake prone region.