The medium under the geoelectrical resistivity station is simplified as a model of horizontally homogeneous layer medium. The disturbance current on the earth's surface is substituted with a point current source. The influence quantity for the geoelectrical resistivity measurement is calculated for a symmetrical four-electrode resistivity observation configuration(a fixed quasi-Schlumberger) when the size and position of disturbance current are changing. The calculated results suggest that the influence quantity caused by disturbance current of the earth's surface is determined by the size and azimuth of current,and the distance from the center of the survey area. The result is important forthe abnormal verification of disturbance current.