The Yanshanian granite in the Sumochagan area, emplaced between Erlian haote-Hegenshan and Suolunshan_Xilamulun River deep_rooted faults, is rich in K, Al, Rb, Th and LREE, and depleted in Sr, Ti, P and Eu, belonging to the high-K calci-alkaline peraluminous granite. εNd（t）ranges from 0.77 to －4.65, t2DMranges from 869 to 1310 Ma, which is similar to things of the granite of ancient microplate in the Hingganling_Mongolian orogenic belt. The μ values of Pb isotope range from 9.2 to 9.5, with an average of 9.37. The ratios of 206Pb/204Pb range from 18.114 to 19.150, with an average of 18.658, those of 207Pb/204Pb range from 15.517 to 15.598, with an average of 15.556, those of 208Pb/204Pb range from 38.384 to 39.054, with an average of 38.614. All these data are plotted in the area between the mantle and the orogenic belt. Geochemical characteristics of the Yanshanian granite formed in a post_collision extensional tectonic envir onment indicates that the Yanshanian granite is a product of the mixture of the crust and the mantle substance. The Yanshanian granite is very closely related to fluorite and base metal mineralization in the Sumochagan area.