Experiments on the mixture of two type gases or different stage gases indicate that the mixture alkane gases have the isotopically heavier carbon and lighter hydrogen with the decrease of oil-type gas mixture, and the three-stage model of stable isotope fractionation occurs. The geochemical pattern of the quantitative identification of the mixing of coal- and oil-type gases was established, and this pattern was successfully used in the Yakela gas pool, suggesting that the gas would be main oil-type gas, and mixed by 12%~20% coal-type gas. In the mixing simulation of different mature gases from the same source rocks, the carbon isotope compositions of alkane gases gradually become heavier with increase of high mature gas mixing. Then we established the geochemical pattern of the quantitative identification of the mixing of oil-type gases at different thermal stages. This pattern was used in the Tahe oilfield and indicated that the mixing of natural gases at high- and low-mature stages existed in the Tahe oilfield, with main high mature gas in the eastern part of Tahe area and low mature gas in the western part. The mixed proportion of low-and high-mature gases in the eastern and western parts ranged from 1 to 19 and 13.3 to 1, respectively. The filling direction of natural gas in the Tahe oil field was from southeastern to northwestern, and eastern to western. According to marine strata feature of south China, the amended dating model of the gas source rock was setup by argon isotope accumulation effect and used to quantitatively identify the gas source in the well Dawan 2 of the northeastern Sichuan basin.