Abstract: Based on the data of seismic, formation test, logging and core analysis, the paper systematically analyzes the characteristics of the low oil-saturation reservoir in the first member of Hutubihe formation in Wellblock Lu-9, Luliang oilfield. The results show that the reservoir is characterized by low amplitude, multiple stratigraphic series, one reservoir in one sand body and active edge and bottom water. The reservoir distribution is controlled by structure and lithology and relatively wide oil-water transition zone generally exists in the reservoir. The low oil-saturation reservoir formed far away from hydrocarbon generating center with complicated accumulation process, leading to insufficient differentiation of oil and water in traps, which is the main reason for the low oil saturation of the reservoir. Additionally, low structure amplitude, wide distribution of clay minerals and high saturation of bound water in the reservoir are the reasons resulting in insufficient pore water displacement by hydrocarbons and low oil saturation of the reservoir