In this paper,relationship between natural geoelectric potential observed at Jiashan station of Anhui Province and moderate earthquakes(M_L ≥ 4.5,△ ≤ 300km)around this station has been studied based on the all curves of daily means from 1974 to 1993. According to the field experiment results in 1979,the better response of natural potential to the moderate earthquakes in the 1970_s is probably caused by the positions where west measuring electrode is sensitive to earthquake preparation. In the seismogenic process,the variations of regional tectonic stress field result in changes of the level,physical properties and chemical constituents of ground water around the west measuring electrode,thus make natural potential E_WE rise or drop by a big margin.