The tight oil is different from the conventional reservoir, and the boundary between oil and water is obvious.Generally, the oil saturation increases with the increase of porosity, and the closer to the source rock, the higher the oil saturation.Therefore, the oil-bearing thickness cannot be simply expressed as the height from the top of the oil layer to the oil-water interface,and the influence of fractures on oil-bearing saturation should also be considered.In this paper, according to the characteristics of the main filling power of tight oil to increase pressure for hydrocarbon and capillary pressure difference, combined with the factors affecting fractures, and by applying the principle of seepage theory, a calculation formula for the direct infiltration of oil from hydrocarbon source to the depth of tight reservoir is established,and the oil thickness of tight oil is calculated by weighted average method.Taking 3 wells of CNPC as an example, the oil content thickness of tight reservoirs in each well is calculated to judge the oil content.The practical effect is good, which provides a basis for the evaluation of oil content thickness of tight oil in a large area.