As commercial risk of oil and gas exploration of the world increases

commercial evaluation on source rocks has become more and more important. Till now there isn't a good method to evaluate high matured carbonate source rocks

especially of gas source rocks. Quantitative evaluation criterioa for gas source rocks is introduced in this paper.According to the conception of effective gas source rock

rock isothermal absorber is used to abtain maximum of absorptive gas

then use thermal analogy analyzer to measure the pyrolytic gas amount of the rock. If the pyrolytic gas amountis greater than the maximum of absorptive gas of the rock

the rock then could be considered as available gas source rock. The criterion of high-matured carbonate rocks is established as effective gas source rocks by a lot of experiments.Gas generation rate of l5 l/t is considered to be the lower liwit of the carbonate. source rocks. This criterion is applied to evaluate the available carbonate source rocks in Tarim

Ordos and Sichuan basins

and is proved to be effective.