The authors analyze the relation between the precursory fields such as the deformation stress field and the post-seismic effect field of water level with the earthquakes ever occurred in Fujian area on the basis of the data from the precursor network in Fujian Province, and find that many ML4.5 earthquakes occurred in Fujian area were accompanied by the formation of the deformation stress field and post-seismic effect field of water level. When the migration of the field of post-seismic effect of water level and field of deformation stress are identical, the related area has the probability of medium-strong earthquakes’ occurrence. Analyzing the migration of post-seismic effect of water level and crustal deformation, the authors may predict the location of the earthquakes.