Abstract: Since 1979 repealed observations and experiments of geomagnetic total intensity and its vertical component have been carried out for ten years at the geomagnetic network which is located over Jiangsu Province. In this period the geomagnetic effects of three earthquakes were observeted. The observation results show that no anomalies of the vertical component of geomagnetism have been observed as long as earthquake of Ms>5.0 have not occurred.In this paper, it is suggested that a dense network for continuous observation of the vartical component of geomagnetism may catch geomagnetic anomalies associated with earthquakes of M>5, and this may improve effectiveness of earthquake prediction by geomagnetic observation at mid-or-low latitudes locations.