Abstract: Based on the published paper of present author(Ruan ＆ Xu, 1996)and Siegel’S model of polarizability, this paper first derives a direct inversion method for interpretation of IP sounding curves. Then according to the works of Zohdy(1989) and Oldenburg(1991), a contrast iterated inversion method in the interpretation of IP sounding cur was presented to improve the inversion precision. The interpretation for the given IP sounding data shows that these methods are excellent.