Abstract: Using 3-D magnetosphere inverse theory and method, we process the aeromagnetic data:of Yanqing and Huailai areas, and obtain the buried depth map of Curie isothermal surface and the distribution map of apparent specific magnetizing moment of these areas. The quantitative characteristics of the magnetic basement of the four correlative basins-Yanqing, Fanshan, Huailai and Zhuolu-are revealed. Investigation is conducted into the deep cause for earthquake occurrence and into the relation between crustal blocks with different physical nature and seismicity in these areas. Characteristics, of earthquake distribution in these areas is also studied. Earthquake risk zoning and major zones for future monitoring in these areas are preliminarily POinted out.