Gaoyou sag in Subei basin is rich in oil and gas resources and has good exploration prospects. Based on the detailed analysis of crude oil physical properties, the geochemical characteristics of saturate and aromatic hydrocarbons, the sedimentary environment, source input and maturity of crude oil from several typical oilfields in Gaoyou sag were studied, and the different genetic types of crude oil in Gaoyou sag were determined. It is found that the crude oil in Gaoyou sag comes from the reducing environment with high salinity, and the source of organic matter is a mixed source, which belongs to mature crude oil. According to the sedimentary environment, parent material source and maturity characteristics of crude oil, the genetic types of crude oil can be divided into two categories: the first type of crude oil generally has a low planting ratio, the ratio of C158β (H) -drimane / C168β (H) -homodrimane is generally close to or greater than 1, the ratio of C21TT / C23TT is low, the ratio of C24 tetracyclic terpane / C26 tricyclic terpane is small, the ratio of C29 norhopane / C30 hopane is low, and the distribution of regular steranes C27, C28 and C29 is asymmetric "L", The sedimentary environment of crude oil is reductive environment. The parent material is mainly from mixed type, and the input of higher plants is slightly higher. It belongs to mature crude oil. This kind of crude oil is mainly distributed in Chian, Chenbao, Wazhuang, Shanian and other oilfields; The above parameters of the second type of crude oil are completely opposite to the first type of crude oil, and the reduction degree of the sedimentary environment of this type of crude oil is slightly lower than that of the first type of crude oil; The source of parent material belongs to the typical dual input mixed type. Compared with class I oil, higher plants account for less and belong to mature crude oil. This kind of crude oil is mainly distributed in Majiazui, Shaobo, Xuqian 1 and Huangjue oil fields.