Abstract: The research on long-term precursory anomalies shows that the beginning, ending and evolution of the long-term precursors are related to those of a seismic period and strong seismicities.The long-term precursors appear in some order in recent years, for example,the precursors moved from east to west and the shocks took place first in the east and then in the west.Therefor the long-term precursors might display the evolution, expansion and immigration of the regional stress field and the correlation between the earthquakes,by which we can judge the beginning and ending of a seismic period and predict the following shocks.The results provide a new way for the study on dynamics in seismicity and to determine seismic tendency.

Key words: Long-term precursor, Evolution of stress Field, Seismic period, Dynamics in seismicity