Abstract: This study analyzes the carbon - hydrogen isotope and light hydrocarbon compositions of natural gas in the Upper Paleozoic strata of Sulige gas field, Ordos Basin. Evidence shows that natural gas in this basin is coal-derived gas from the Carboniferous-Permian coal measures. Then, a comparative analysis is conducted on natural gas in the Upper Paleozoic strata in Sulige gas field and those with similar maturity but different depositional environment and similar depositional environment but different maturity. Results show that the hydrogen isotope value becomes heavier with the transition of depositional environment from lacustrine, terrestrial, and paralic to marine environment, as well as with increasing maturity of natural gas. Thus, maturity should be taken as an important factor in application of hydrogen isotope analysis for identification of depositional environment. Natural gas in Sulige gas field is associated with partial reversal of both carbon and hydrogen isotope compositions which mainly due to the mixing of coal-derived gases from cumulative hydrocarbon accumulation at different stages.