A method of determining and examining earthquake risk region has been developed in this paper. After a strong earthquake, the energy propagated to the neighbourhood, It will become a triggering force to another earthquake in neighbouring region. Under the effect of the triggering force, the small and moderate earthquakes may easy occur in the low strength medium region, but in the high strength medium region the earthquake isn't easy to occur. Thus, the seismic gap may be shown by the small and moderate earthquakes. The high strength region (or seismic gap)can be regarded as future earthquake risk region. We can also examine the truthfullness of the seismic gap using the other earthquakes in succession.