A gold tube simulation device was used to study the cleavage of representative compounds into gas. The goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during maturity. Gas chromatography and isotopic analyses were conducted to determine how the yield of natural gas components and their hydrogen isotopic composition were related to experimental temperature and heating rate. A chemical kinetic model for the generation of each component of the natural gas and for the hydrogen isotopic fractionation was established and calibrated based on the results. Results indicate that the hydrogen isotopic fractionation during the evolution of various gas-forming organic materials can be satisfactorily described by chemical kinetic models. During regular methane generation, the reactions at low–activation–energy region had a greater contribution than the high–activation-energy region. While the reactions with high–activation-energy region had greater contribution of deuterium-rich methane. Compared with carbon isotope fractionation, this results in a greater hydrogen isotopic fractionation, which is more sensitive to changes in maturity. This study lays a foundation for further investigations of genesis and maturity of natural gas provided by hydrogen isotopic fractionation. It also provides fundamental knowledge for investigating the filling history of natural gas reservoir and for identifying.