Abstract: Crude oil of the unit Ⅰ,Ⅱ and Ⅲ of the Shahejie Formation in the Lengdong-Leijiaarea is dominated by heavy viscous oil The study of the heavy viscous oil plays an important role in establishing a fluid characteristic distribution and geochemical model of thearea. In this paper, various experimental data from the analysis of the family components,gas chromatography(GC)and stable carbon isotope of crude oil,and the gas chromatogra-phy-mass spectrometry(GC-MS)of saturated and aromatic hydrocarbons is used to studycomprehensively the geochemical characteristics of heavy viscotis oil in the area. Combining vvith the regional geology and geochemical condition of the area,the oil sotirce condition and genesis of heavy viscous oil are also discussed.The restilt provides an importantgeological basis for the exploration and development of heavy viscous oil pools in the area.