Taking paleoearthquakes,historic and recent earthquakes as time domains,and North China,Shanxi seismic zone,Hebei plain seismic zone and Tancheng-Lujiang seismic zone as units,authors analyze and study the recurrence intervals and migration characters of great earthquakes in North China.On this basis,a dynamic problem of seismic activity,block frame motion,earthquake migration and seismicity trend in North China are discussed.