Petrological and petrochemical characteristics of samples from four Neo-Archean banded iron ore deposits of Baiyuli, Baizhiyan and Ekou in Wutai Mountain area and Qian'an in eastern Hebei Province are reported in this paper. Some comparisons are also made with Anshan iron deposit in Liaoning, Hanwang iron deposit in Shandong and some other iron deposits of the same kind abroad. The authors have found that these iron deposits have highly consistent characteristicss in the following four aspects: all of the samples are depleted in Th, U, La, Ce, P and Sm and enriched in K, Nb, Sr, Hf, Er and Ti; as one of the characteristics of Archean marine sediments, they all have very low REE content, with the average values of the iron deposits in the four areas being 27.65×10-6, 14.56×10-6, 19.03×10-6 and 16.46×10-6 respectively; all of the iron deposits in the four areas are depleted in light rare earth elements and enriched in heavy rare earth elements, with Pr/Yb ratios in the range of 0.81～1.84, 0.35～1.21, 0.76～1.33 and 0.95～1.92 respectively; they have obvious positive anomalies of Y and Eu, with ratios of Eu/Eu* being 2.55～3～36, 2.07～2.25, 1.44～2.56 and 1.43～3.77 respectively, suggesting characteristics of sea water and high temperature seafloor hydrothermal solution. Therefore, the Fe-Si formations were probably formed in a hot sea water environment. In addition, as the values of δ34S of pyrite associated with BIF are close to zero, the authors hold that the sulfur might have come from the mantle. It is thus concluded that the studied BIF are chemical sedimentaryore deposits formed in a high temperature sea water environment after the derivation of silicon and iron from mantlederived volcanic eruption or exhalation.