Abstract: Weizhou Sag 11 in Weixi'nan Depression is a new exploration survey, in which two oil-bearing structures have been discovered. It's confirmed that the sag has great exploration potential. However, there is still a lack of systematic research on the key reservoir formation issues: hydrocarbon source development characteristics, favorable exploration layers and oil and gas migration directions, which leads to the exploration direction is blurry. In order to clarify the favorable exploration direction of the area, this article focuses on the analysis of the oil and gas accumulation conditions and main controlling factors in Weizhou Sag 11 based on drilling, 3D seismic data and laboratory analysis data. The results show that: Weizhou Sag 11 is of good hydrocarbon source conditions and the characteristics of near source accumulation, which is determined by fault-source configuration relationship. A large scale of fan delta reservoir is well-developed in the second member of Liushagang Formation of Weizhou Sag 11. Based on the characteristics of drilled reservoirs and the development of fault systems, it is indicated that the structural ridge line of the western slope of the depression is the dominant direction for oil and gas migration in the sag 11. The article is the first to conduct a detailed study on the accumulation conditions of Weizhou Sag 11, clarifies the main controlling factors of reservoir formation, and points out the favorable exploration directions. The research results provide favorable guidance for the further exploration of Weizhou Sag 11.