Based on the electrochemical theory of IP effect, the coupled partial diffe
rential equation describing the temporal and spatial variations in the conc
entrations of ions can be written out by studying the patterns of the ions'
motion on the interface. According to the structure of the electrical doub
le layer and the stationary solution of the equations, we derive a nonlinea
r diffusion equation supplemented by relevant initial and boundary values,
and put forward a theoretical model of IP. We have obtained numerical solut
ion in time and frequency domain respectively with the help of computer usi
ng the difference approximation. These results revealed the induced polariz
ation properties of minerals. The results calculated from this model prove
that this theoretical model can describe the IP effect correctly in linear
and nonlinear regions.