Abstract: Using the geochemical analysis of sandstones from the Ordovician Miboshan Formation and combining with the regional geology of the Helan Mountain, this paper approaches the tectonic setting of the Helan Mountain during the Middle-Late Ordovician. The geochemical study of the sandstones from the middle section of the Helan Mountain suggests that the sandstones have average SiO2 content of 81.3%, Al2O3/ SiO2 = 0.07 - 0. 11 (average, 0.08), KzO/Na2O = 4. 79 - 7.81, low F2zO3 +MgO contents of 2. 1% 2.81%. The sandstones have relatively higher contents of Nb and higher ratios of V/(V+Ni), Ce/La and Sr/Ba, indicating a humid tropical, reducing and low salinity environment during the deposition of the sandstones, suggesting characteristics of the continent-type sedimentary origin. The sandstones are enriched in rare earth elements, with total REE contents of 116-195 ppm (average, 158 ppm), and promi- nently negative Eu anomalies of 0.52-0. 58. All the geochemical data indicate that the Miboshan Formation shows characteristics of the quick accumulation of gravity current and large terrigenous supply, the turbidity sedimentation is the main way to carry terrigenous materials. The analysis of various tectonic setting discrimination diagrams shows that the geological structure of provenance exhibits a nature of passive continental margin.