Abstract: Bauxite is one of the important strategic minerals in China. The area stretching from South Chongqing to North Guizhou is a famous aluminum-forming region in the upper Yangtze landmass. The adjacent northeastern region of Yunnan is located in the carbonate platform of the passive continental margin in the southern part of the upper Yangtze landmass, which is a favorable location for aluminum mineralization, but there has been no breakthrough in discoveries. In recent years, based on the 1∶10 000 mineral geological survey, through surface survey, profile, exploratory trench, drilling, and comprehensive research, the author's team discovered a large bauxite deposit in Taiyangba, Daguan County, northeastern Yunnan, for the first time. The orebody extends relatively steadily, with a thickness ranging from 0.82 to 30.85 meters and an average thickness of 2.14 meters. The ore is primarily composed of hard alumina, categorized as water-type bauxite, with an average grade of 59.03% Al₂O₃, 19.03% SiO₂, and an A/S ratio of 4.36. The estimated resource size reaches a large scale. The ore deposit is classified into primary sedimentary type (mainly) and secondary accumulation type. The distribution of the ore deposit is mainly controlled by the sedimentary facies belt (shore marsh facies belt) of the Liangshan Formation (P₂l) and the Xinzhaizi syncline structure, which has similar metallogenic conditions with the aluminum-forming region adjacent to the area stretching from South Chongqing to North Guizhou. The discovery indicates that the Daguan area is an aluminum-rich basin, expanding the scope of the aluminum-forming region on the western margin of the upper Yangtze landmass. This breakthrough in ore prospecting will inevitably drive the exploration of surrounding bauxite deposits, lay a foundation for the construction of an aluminum resource base in northeast Yunnan, boost the formation of a new economic pillar industry in the region, and promote rural revitalization.