The juncture region of Hebei,Shandong,and Henan provinces (Ji-Lu-Yu region for short),where many middle-strong earthquakes have occurred throughout history,is the focus of this study as an earthquake risk area.We used 20 stages of mobile gravity observation data,gathered from 1995 to 2010 in the region,to calculate the accumulated variation in the gravity field by means of a quasi-stable adjustment,on the basis of a unified calculation datum and elimination of system error.By analyzing variations in the gravity field before and after five earthquakes,the relationship between the dynamic variation in the gravity field and a series of M_L>4.0 earthquakes was studied.The earthquakes studied were the M_L4.3 earthquake,April 27,2005,epicenter located between Puyang in Henan and Juancheng in Shandong; the Puyang M_L 4.6 earthquake,April 9,2006; the M_L4.3 earthquake,January 3,2008,located between Fengqiu and Lankao in Henan; the M_L4.8 earthquake,March 10,2008,located between Fengqiu and Lankao in Henan; and the Puyang M_L4.2 earthquake,January 15,2010,The results show that,in this region,the gravity field variation shows a certain regularity before and after earthquakes of magnitude>4.0.This characteristic is obvious in that "gravity values rise continuously before earthquakes and reverse after". In addition, reasons for the regularity in the gravity field variation before and after earthquakes are investigated in this article.