The seismic data from 1972 to 1992 in North China are used in spacial scanning of seismic risk degree D-value in this paper.The result shows that there are large anomaly zones of D-value around the future epicenter about 3 years before most moderate-strong earthquakes.In this paper,the method using D-value in medium-term earthquake prediction,prediction ability,the relation of D-value to real seismicity and the stability of computation are also discussed.