Abstract: A set of sedimentary strata, which is rich in fossils such as Ostracoda, vertebrate and numerous plants, outcrops in Xiaotaizi area of Jianchang County, western Liaoning Province. With study on the regional stratigraphy, combining with the survey of 1:2000 geological profile and collection of fossils, especially plant fossils, in each horizon, it is concluded that the set of strata is above Yixian Formation, belonging to Jiufotang Formation. Formed in Early Cretaceous, its features of biological fossil assemblage are consistent with those of the late community of Jehol Biota.