Abstract: The Yongshun-Longshan area in northwestern Hunan Province was an area of deltaic sediments from Longmaxi Formation of Lower Silurian. The deltaic sedimentary system can be divided into predelta, deltaic front and deltaic plain facies. The predelta was composed of the Longmaxi Formation, in which three microfacies were identified: in-situ shale and mud, turbidites and bottom-current deposits. The later two facies mainly developed in the lower part of the Longmaxi Formation. The deltaic front was represented by the Xiaoheba Formation, in which four facies were recognized: front and sheet, reef, oolite (bioclastic shoal), inter-reef (shoal) mud. The Rongxi Formation was deltaic plain which includes bracnched channels and marsh. The river for building the delta was characterized by low velocity, high discharge, high concentration of fine clay and sand, and associated with reef (shoal) in delta front.