Abstract: With discussion on the formation mechanism of primary and secondary voltages in induced polarization (IP) exploration on the basis of capacitance property of rock and geological body, this paper points out the improper adoptation of the hypothetical IP theory, thus the phenomenon of primary and secondary voltage should be scientifically applied in geophysical prospecting. According to the fact that all actual resistors have the capacitance characteristics and all capacitors leak electricity, it is presumed that rocks and geological bodies as resistors also have capacitance. The equivalent circuit of resistance and capacitance in rocks and geological bodies verify that the primary and secondary voltage could be incurred in charge and discharge process, and the sum of two voltages is equal to the voltage when charging is stable. It also certifies that there is phase shift between current and voltage and decreasing impedance with increasing frequency in alternating current charging. Based on the measured data, it is inferred with comprehensive analysis that equivalent circuit-derived primary and secondary voltages are consistent with the actual measurement. The results show that there is no inducing factor in the formation of primary and secondary voltages, and the polarizability in IP theory has nothing to do with polarization. The relation between primary and secondary voltages can reflect the metallic mineral content in rocks and geological bodies, and the time constant of charging and discharging and capacitance characteristics can be effectively used in geophysical prospecting to identify hidden geological bodies.