Shifang-deyang-guangjin area is located in middle western Sichuan Foreland of Sichuan Basin, north and north east of Chengdu Sag. Based on sesmic, geology, drilling, logging, core and test data, discussed the origin and nature of tight gas in Penglaizhen Formation, distribution characteristics, the relationship with sedimentary facies, accumulation time, the time of hydrocarbon expulsion and accumulation characteristics. The results demonstrated that the gas of Penglaizhen Formation in studied area mainly comes from the source rock underlying fifth Xujiahe Formation, which are high quality dry gas without H2s formed in the normal temperature and abnormal high pressure environment. The main accumulation time was middle late cretaceous-early paleocence and the time of hydrocarbon expulsion was the end of late Jurassic-early cretaceous. The gas reservoir of Penglaizhen Formation may be deep in the early or middle gas reservoir by the tectonic movement after the formation of the gas reservoir.