Isotopic composition of 90 natural gas samples, which were collected from north Jiangsu Province, south Songliao, Sanshui County of Guangdong Province, Sichuan Province, the Junggar and Tarim oil and gas-bearing basins, and the Yaojie coal mine of Gansu Province, have been analysed in terms of δ 13C of CO 2 and CH 4, δD of CH 4, δ 15 N of N 2, 3 He/ 4 He, 40 Ar/ 36 Ar and R/R A . Base on the isotopic and and chemical compositions of the natural gas and the geological background of these areas, such aspects as the genesis of non-hydrocarbon gas, geochemical characteristics of noble gases and the correlation of gases with sources have been discussed. In this paper, it is pointed out that hydrocarbon and non-hydrocarbon gases reservoired in the same stratum may be of different genesis; that the helium of the He-rich gas pool of Huangqiao, north Jiangsu is closely related to the mantle; and that the He and CO 2 of south Songliao, Huangqiao of north Jiangsu, and Sanshui of Guangdong CO 2 pool, have some relationship with the mantle. Like the crust sourced argon, helium also shows the chronological accumulating effect.