Abstract: The lithological characteristics and the brachiopods of the Azigan Formation and Tahaqi Formation of Piyaman-Buya area in southwestern Tarim Basin were studied. The brachiopods were assigned to 11 genera including 15 species, belonging to Spiriferida, Productida, Strophomenida and Rhynchonellida. Based on the characteristics of the lithology and brachiopods, the authors hold that, during middle and late Late Carboniferous period, the palaeoenvironment of Piyaman-Buya was warm. The sedimentary facie was carbonate plateau, and the water was shallow and turbulent. During this period, there were two retrogressions, and the sedimentary records were located on the upper section of Azigan Formation and at the top of the Tahaqi Formation.