A survey was conducted in the southern Beishan Mountain to ascertain mineral ypes and distribution. A manganeserich rock bed, 0. 5 m thick at the surface, extending 4. 6 m in the horizontal direction with a bean shape has been discovered in the quartz schist in Changchengian System stratum. Its upper part is Mnlimestone and Mnmagnetite quartz rock, sandwiched between Quartz schist. The manganese ore is black, bulky, semimetallic luster, and also occurs as dirty bands. The results of the manganeserich rock samples by quantitative chemical analysis are Mn 29. 68%, 30. 59%, 27. 72%，Mn/Fe 9. 2, 9. 8, 8. 7，P/Mn is 0. 00071, 0. 00078, 0. 00076. The Mn content of Mnlimestone is 4. 62~4. 92% and of Mnmagnetite quartz rock is 0. 52~1. 54%. Moreover, based on the phase analysis tests, the Xray diffraction the electron probe data, and the microscopic identification, the important minerals are Rhodochrosite (MnCO3), Pyrolusite (MnO2), Manganite（MnO2·Mn(OH)2），Spessartine (Mn3Al2(SiO4)3), Johannsenite (CaMn(SiO3)2), Rhodonite ((Mn,Fe,Ca)5Si5O 15 ), Tephroite ((Mn2SiO4)), and some other minerals, have been determined. A global comparison of the characteristics and mineral assemblages of this ore shows strong similarities with the Paleoproterozoic Serra do Navio manganese deposits in Brazil, the Devonian metamorphosed manganese deposits of the South Urals, and the Cretaceous NodaTamagawa Mine in Japan. Based on fieldwork, Mn content and the special mineral assemblages we propose that: (i) the manganeserich rock was possibly deposited in the shallowmarine and marine environment around the Dunhuang ancient block edge areas. The manganese was derived from the continent and the hydrothermal fluid sources. (ii) Subsequently, in a period of regional metamorphism and contact metamorphism, sandstone had metamorphosed into quartz schist, the ores of Rhodochrosite and Pyrolusite and Manganite, as the primary high quality manganese ores, had become into Mnsilicate. (iii) After prolonged supergene weathering, the manganeserich rock presently seen were formed. (iv) The discovery of manganeserich rock indicates that there is a metallogenic geological environment for the formation of manganese deposits in this area.