Abstract: The occurrence of oil and gas is discovered in the Beipiao Formation of SZK04 well located on the western margin of Zhangjiyingzi Sag in Jinyang Basin. The organic geochemical analysis results show that such oil sands are characterized by low pristane-phytane ratio, abundant hopane compounds, high gammacerane content, deficiency of sterane compounds and light carbon isotopes. Combined with the biomarker compounds and carbon isotope values, it is believed that the source rocks deposited in marine reduction environment should contribute to the oil sands of SZK04 well, with the organic matter mainly from bacterial input. Considering the geological background of the area, it is concluded that the type of marine oil sands may come from the MesovNeoproterozoic source rocks, which provides a basis for the Meso-Neoproterozoic oilvgas exploration in Jinyang Basin and even the western Liaoning Province.