Gas sources of Ordovician weathered crust gas reservoirs in Central Gas Field in the Ordos basin are an important problem that has not been completely solved. On the basis of a large number of previous research, geochemical characteristics and indexes of mixed origin natural gases i~om Ordovician weathered crust gas reservoirs in Central Gas Field in the Ordos Basin are systematically studied. The gas sources from this gas field are also discussed through the comprehensive analyses of many indexes. The results demonstrate that natural gases from Ordovician weathered crust reservoirs in Central Gas Field in the Ordos Basin have the characteristics of gas components and isotope compositions of high mature and over-mature dl7 gases. In Central Gas Field in the Ordos Basin, there are both coal-ibrmed gas and oil-type gas, the ibrmer of which comes from Permo-Carborrfierous coal measures and the latter originates from lower Paleozoic marine carbonate. The coal-ibrmed gas is mainly located in the eastern part of Central Gas Field while oil-type gas lies in the northern, western and southern parts of Central Gas Field in the Ordos Basin.