The Mesozoic strata of the Yanqi Basin consists of coarse debris with coal beds, characterized by the developments of coal seams of the Jurassic sediments whose main petrologic contents are glutenite, fine sandstone, mudstone, carbonaceous shale and coal. Based on the analyses of the minerals, trace elements and REEs, we try to find geochemical characteristics of the coal seam formation process. The analysis results indicate that the contents of ash and sulfur are low while the content of phosphor is comparatively high, and that the specific value of Al2O3/SiO2 is relatively high and that of (Al2O3 + SiO2)/(Fe2O3 + CaO+ MgO) is near 1. All these results indicate that the coal seams are formed in the relatively deep marsh, which is favorable for the evolvement of hydrocarbon at the diagenesis stage. The Mesozoic strata of the Yanqi Basin consists of coarse debris with coal beds, characterized by the developments of coal seams of the Jurassic sediments whose main petrologic contents are glutenite, fine sandstone, mudstone, carbonaceous shale and coal. Based on the analyzes of the minerals trace elements and REEs, we try to find geochemical characteristics of the coal seam formation process. The analysis results indicate that the contents of ash and sulfur are low while the content of phosphor is comparatively high, and that the specific value of Al2O3 / SiO2 is relatively high and that of (Al2O3 + SiO2) / (Fe2O3 + CaO + MgO) is near 1. All these results in the coal seams are formed in the relatively deep marsh, which is favorable for the evolvement of hydrocarbons at the diagenesis stage .