Porphyry ore is one of important iron ore deposit types in China, and it is the iron ore deposit in the andesitic and diorite porphyry which rich in sodium, but not easy to determine the location and ore occurrence because of the influence of conventional geophysical exploration caused by volcanic, so it is not easy to determine the location and ore occurrence, and the prospecting is difficult. Electromagnetic exploration method has the characteristics of great depth and high resolution, so it is a possible mean to detect porphyry ore. To assess the effect of electromagnetic methods applied in the detection of porphyry ore, the authors combine the known geological data and construct the theoretical electrical model of porphyry ore on the basis of statistical properties, then discuss the effects and resolution of audio magnetotelluric, controlled source audio magnetotelluric, transient electromagnetic and complex resistivity methods used in porphyry ore exploration by model forwarding and inversion. Then launch a test with four electromagnetic methods taking Nihe iron ore in Anhui as example, and obtain the three dimensional electrical model of Nihe ore zone, which reflects the basic information of stratum, rock and structure. Although it cannot indicate the ore body position directly, the important clues are provided for prospecting work by the delineation of diorite pluton uplift range. The test results show that, the high quality of the data processing and efficient inversion method for electromagnetic method is an important guarantee for porphyry ore. And electromagnetic exploration examples in Nihe iron ore can provide guidance to the lower reaches of the Yangtze River porphyry ore prospecting.