The reservoir interlayer is an important factor in the flow in the reservoir. The reservoir interlayer and the characterization of the oil field are closely related to the oil distribution remained from the mid-later period and the development of the oilfield. Based on the core observation, in view of the Tarim basin in Donghe Marine sandstone reservoir in Tazhong area, this paper analyzes the mechanism of the origin of the interlayer, which is divided into two major types, formed by deposition and diagenesis. With electrical characteristics comparisons and the data of physical properties, three types of interlayer are identified, including mud, calcium and properties, and an inter-layer identification standard of non-core wells is established. Its role in the control of the oilfield development is discussed from the aspects of the thickness, distribution, vertical permeability and the attitude of the interlayer. The sealing capacity of oil and water of the interlayer has positive relationships with its thickness and distribution. Vertical permeability decides the degree and speed of the injection water moving up and down. Water injection along the tendency direction of the interlayer is often liable to form the remaining oil-rich region.