Abstract: As a special kind of unconventional gas resources with great resource potential, gas hydrate is not only an important supplement and substitute for conventional natural fossil gas, but also a new low-carbon green and efficient energy. In order to better understand the special geological formation conditions and distribution pattern of the gas hydrate, the geological and geochemical characteristics of the global gas hydrate and their sources were studied in-depth by the authors. According to the statistical results of the geochemical compositions of natural gas hydrate explored in the world so far and their geological formation conditions, the main genetic types of gas hydrate are biogenetic and biogenetic-pyrolytic mixed, followed by matured pyrolytic gases in terms of the sources of gases. The formation of gas hydrate deposits depends on the sources for gas supply in addition to a high-pressure and low-temperature environment.