Abstract: The late-carboniferous reef in the Keziliqiman area located in the Pishan County. south margin of Yecheng depression. Tarim Basin , is one of reefs , found in the Basin, being intactly reserved , rich of frame-building living beings and typically developed. Finding of the reefs not only enables exploration of reef-type oil and gas reservoirs in south flank of Hetian fault. but also there must exist a deep water oil generation deposition center (troughopen platform) accompanied in north flank of the fault ( reef front ). Reef front is favorable for oil generation. Reef core is favorable for oil gethering. Reef behind and cap can form seals for oil and gas . According to litholopy, biofossils and richness of organic materials and compared to other areas in the Basin. south part of the Yecheng depression is characterised with innate conditions of better tectonic position (mobile edge of continent), thick deposit(3000~4500m) , vast area ( 3000~4000 km² ) and favorable oil generation environment ( trough platform-open platform).