In this paper, the data and seismic examples of the deep-well geo-electrical resistivity experiments in Gansu province in recent years are introduced, and SA scheme (vertical observation scheme of single-hole deep well in Gansu) is proven to have better earthquake precursor detection efficiency. The mechanism and principle of the scheme is explained from the perspective of horizontal layered medium, and the prediction efficiencies of various installations are quantitatively estimated. The analysis holds that SA is the best approach to solve the electromagnetic interference problem, in order to improve the precursor detection efficiency of installations.