Abstract: This paper systematically studies the geochemical characteristics of the upper Paleozoic source rock which is in Xunyi block, south of ordos by stratification and lithology, providing theoretical basis for oil and gas exploration. Based on the sorting and analysis of the existing data of drilling cores, cuttings and chemical analysis in this area, a comprehensive study of degree, type and maturity of the organic matter of the source rocks is done considering the regional geological conditions. The results show that the organic matter type is the Ⅲ kerogen. The maturity is generally from high-mature to over-mature, the majority being over-mature dry gas. Both Taiyuan Formation and Shanxi formation have good hydrocarbon generating potential. The paper also brings carbonaceous mudstone into the evaluation category. The evaluation results show that carbonaceous mudstone has a certain material basis. It has promoted the exploration potential of this area, and enriched the hydrocarbon source rock evaluation theory in the south of the whole basin. It has an important guiding significance for the exploration and deployment of natural gas in this area.