Abstract: In this paper, based on the analysis of various changes of all precursor observational means after the Xingtai, Bohai, Haicheng, Tangshan and Datong earthquakes in North China area, 3 quantitative indexes and 4 qualitative indexes have been summed up. Besides, the method of fuzzy synthetic evaluation has been given. The results calculated by this method conform to reality. When the result of evalution is that there will be an earthquake, the experiential criterion for the three elements of follow-up earthquakes has been given.