In order to seek for metallic orebodies buried at relatively great depth, we should study the great depth induced polarization method. The present paper has made a preliminary discussion on some key problems around the elevation of signal-to-noise ratio, such as the selection of time domain frepuency system, the dual-frequency high power IP system, the great depth IP array technique, and the elimination of coupling effect of electromagnetic induction. This discussion contributes to the research on the great depth induced polarization method.