利用天然气碳同位素资料，解决了气源判识方法和指标问题，并证明鄂尔多斯盆地中部大气田的主要气源层系是下奥陶统，但在气田东部确有来自石炭—二叠系煤系的混源气甚至煤成气存在。根据气源和天然气成熟度的研究结果，把鄂尔多斯盆地北部的天然气划分为４种成因类型：①源于石炭—二叠系的高成熟裂解煤成气；②混源气；③源于下奥陶统的高成熟裂解油型气；④过成熟裂解油型气。后者是中部大气田天然气最主要的成因类型。 Using gas carbon isotope data of natural gas, the method and index of gas source identification are solved, and the main source gas system of the gas field in the central Ordos Basin is proved to be the Lower Ordovician. However, there are indeed coal-derived carbonates from the Carboniferous Permian coal system Mixed source gas and even coal gas. According to the research results of gas source and gas maturity, natural gas in the northern part of Ordos Basin is divided into four types of genesis: ① high mature pyrolysis coal derived from Carboniferous-Permian; ② mixed gas; ③ gas from Lower Austria Tao system of high-mature cracked oil gas; ④ over mature cracked oil gas. The latter is the most important type of natural gas in the Central China Gas Field.