According to numerical simulations, the present paper deals with propertiesof the spsctral IP anomaly when IP and electromagnetic effects coexist, indicatesthe spatial distribution shape and frequency characteristics of IP and electroma-gnetic induction on low-resistivity and high-resistivity polarized object, and veri-fies the reasonability of separating IP effect fIom electromagnetic effect byinversion of apparent complex resistivity frequency spectrum according to com-bination of two Kerr-Kerr models. The results of inversion of theoretical frequ-ency spectrum with this technique are utilized to illustrate the anomalous pro-perties of IP apparent frequency spectrum parameters. In addtion, a discussionis given concerning the effects of overburden and nonisotropy on the anomalyof spectral IP method.