Abstract: The banded iron formation (BIF) of Guocheng town is located in the northeastern margin of Jiaolai Basin, which was occurred in metamorphic rocks of Proterozoic Jingshan group. After comparing with the iron deposits in Qian'an area of East Hebei and Wutai area of Shanxi, it's found that Guocheng iron deposit was formed by chemical sedimentary, with certain amount of involved debris. In the REE distribution diagram of Post-Australian Archean Shale (PAAS), this deposit has depleted LREE, with high Y/Ho ratio and positive La-Y anomalies, indicating that this deposit was precipitated in the marine environment. The high Ti/V ratio and strong Eu positive anomaly stand for the participation of volcanic hydrothermal fluid. Thus, it's believed that the metallogenic material was derived from the volcanic activity. There was no obvious negative Ce anomaly, indicating that there might be an anoxic atmosphere at that time. The hydrogen and oxygen isotopes of ore and surrounding rock indicate that the ore-forming fluids not only sourced from volcanic hydrothermal solution, but also from other fluids.