Limestone interlayers with different thickness develop in thick shale formation of Es1 in Bonan subsag. Learning from the national standard of shale gas and SINOPEC standard of shale oil,the thickness of interlayer that produces oil was determined. The criteria,the thickness of single interlayer is less than two meters and the cumulative thickness of interlayer is less than 20% of that of the formation,were regarded as the recognition standard for interlayer shale oil in Bonan subsag.The interlayer at the lower part of Es1 mainly consists of dolomite and its log response is characterized by obvious high resistivity. The water cut is gradually increased in the process of oil and gas output,which supports the point that the shale oil from interlayer mainly exists in free state. By analyzing the correlation between production capacity and enrichment factors of interlayer shale oil,it is found that whether interlayer shale oil can effectively accumulate is mainly controlled by four factors including generation and discharge condition of hydrocarbon,thickness of interlayer,physical conditions of interlayer and formation pressure and oil properties.