Abstract: The Datie bauxite deposit in Qiubei County, southeastern Yunnan Province, is a recently-discovered medium-size sedimentary diaspore deposit, and its ore-hosting strata are developed in the lower member of Upper Permian Longtan Formation. Through an analysis of mineralogy and petrography, the authors conducted a systematic research on the compositions and modes of occurrence of the ore minerals. The result indicates that diaspore is the main mineral, followed by kaolinite, illite, sericite, chlorite, anatase, goethite, hematite, rutile, chalcedonite, etc., presenting a diversity of crystalline morphologies and modes of occurrence. Five main dissemination characteristics of diaspore are observed: a) unevenly disseminated in gangue minerals with euhedral or subhedral granular textures ; b) in pisolitic, potato-shaped or oolitic forms; c) as aphanitic crystalline or microcrystalline aggregates or with irregular granular or microgranular texture; d) as veins, skeletal crystals; e) as aggregates of diaspore, alumina gel or gangue minerals assuming zonal patterns or concentric circles.