Abstract: Basing on the analysis of the characteristics of the seismic activity before the moderately strong and the larger earthquakes occurred in the Capital Circle area (35.5°一41°N,113°~120°E),this paper sums up the universal characteristics of the seismic activity before the moderately strong and the larger earthquakes in this areaa, makes a comprehensive analysis of seismic activity anomalies by seismogenic model and gives the physical basis of earthquake prediction by seismic activity anomalies.This paper also proposed the comprehensive distinguishing index of earthquake prediction by mid-term anomalies of seismic activity When it reaches the given threshold value, then according to the geologic structure, the natural probability of occurrence of moderately strong and the larger earthquakes, the earthquake-reducing action after a large earthquake, the distribution of mid-term amomalies of seismic activity and its prediction effectiveness, the two-dimmensional comprehensive probability distribution map can be given,the area with higher probability value can be considered as a risk area of a moderatly strong or larger earthquake in the coming one or two years.Furthermore, the study of the magnitude and time prediction has been made.