Overburden by wide-distributing Middle Cambrian Qinjiamiao salt rock, both Lower Cambrian Shilongdong and Upper Sinian Dengying hydrocarbon-bearing reservoirs are the important exploration targets in the western Hubei-eastern Chongqing area and adjacent area. However, it has been doubtful to the fact if the hydrocarbon in these reservoirs derived from both the Lower Sinian Doushantuo and the Lower Cambrian Tianheban-Niutitang source rocks because of their high t hermal evolution. According to the effect analysis of replaceable gas source, it is shown that the high-matured to over-matured hydrocarbon kitchens are of the pre-Indosinian kerogen-pyrolyzed and Indosinian-Yanshanian oil-pyrolyzed hydrocarbon sources. The fluid behavior tracking to C , O and Sr stable isotope marks supports the theory of continual y filling of multi-period hydrocarbon sources which provide greatly huge amounts of hydrocarbon. By account, the effective hydrocarbon amounts can reach to 15,554.89×109m3 in Dengying reservoir and 58,925.576×109m3 in Shilongdong reservoir respectively, which means that there is good gas resource potential in the western Hubei-eastern Chongqing area.