The Jingtieshan Iron (copper) deposit is the large iron (copper) deposit discovered and explored earliest in Northwest China. There are still different views on the genesis of iron deposit. The petrological and petrochemical characteristics of the ore bearing strata of the deposit are analyzed. The average contents of SiO2, Al2O3, Fe2O3, SiO2/Al2O3 and K2O/Na2O ratio of metamorphic quartz sandstone is 96.95%, 1.36%, 0.31%, 73.26 and 12.54 respectively; Except Sn, the average contents of Trace and rare earth elements are lower than the Post Archaean Australian Shale (PAAS ) value, with weak Eu positive anomaly and no obvious Ce anomaly. The average contents of SiO2, Fe2O3,SiO2/Al2O3 and K2O/Na2O in the metamorphic quartz sandstone are 85.67%, 10.19%, 430.47 and 0.79; Cu, Ba and Pb were significantly higher than PAAS value; it has obvious Eu positive anomaly, and has not obvious Ce anomaly .The average contents of SiO2, Al2O3, Fe2O3, K2O and MgO in phyllite are 63.56%, 14.35%, 5.04%, 5.08% and 2.46%, respectively; SiO2/Al2O3 is relatively stable, and K2O/Na2O ratio vary significantly; The contents of Trace and rare earth elements are high. Most of the components are higher than PAAS value except Cu, Sr and U, and Inconspicuous Eu and Ce abnormalities. It is considered that the phyllite and metamorphic quartz sandstone of the Lower Rock Formation of the Jingtieshan Group are terrigenous sedimentary and igneous rocks, which have undergone moderate to strong weathering under semi- arid and humid climatic conditions and deposited in the oxidation—dysoxic —suboxic water environment on the passive continental margin. The iron jasper rock is formed in the oxidized water environment and is a typical hydrothermal origin. The Jingtieshan iron deposit is a SEDEX- type deposit, which is related to the breakup of the Columbia supercontinent.