It is known that a great amount of natural gas hydrate exists under deep sea floors and hydrocarbon sources of many known huge oil and gas provinces in the world are associated with paleogeosyclines. It is inferred that gas hydrate could have existed under paleosea floors such as deepsea troughs and their sides during geological history. It is deemed that the a large quantity of natural gas reserves that are present in Sichuan Basin could be hardly supplied all by the known source rocks, so some of the gas reserves might be derived from the gas released and migrated by gas hydrate within deepwater geosyclines along the northern and western continental margins of Upper Yangzi Massif during inversing orogeny (Chinling and Longmen mountains formed). Resembling hydrocarbon prospecting areas as it can be also inferred for reference.