Abstract: The section of the Dabeigou Formation at Yushuxia Village, Zhangjiagou, Huodoushan Township, Luanping County, Hebei, is characterized by the continuation of strata, clear top and bottom and abundant contained fossils. The formation consists predominantly of sedimentary rocks with small amount of volcanic rocks and may be divided to three members from the bottom to top. The first member contains sporopollen, and the second and third members contain very abundant fossils, including conchostracans, ostracods, bivalves, gastropods, Limulus, fishes and plants. Of these, conchostracans, which are distributed in at least 25 fossil beds from near the bottom up to top of the Dabeigou Formation, include 5 families, 9 genera and 36 species. Among these, the genus Nestoria predominates and occurs throughout the Dabeigou Formation, so these fossils may be called the Nestoria fauna. The Nestoria fauna may be further divided in ascending order into three conchostracan zones: the Nestoria pissovi-Jibeilimnadia ovata assemblage zone in the lower part, and the Nestoria pissovi-Keratestheria gigantea assemblage zone and Yanshania xishunjingensis-Yanshania subovata assemblage zone in the upper part of Dabeigou Formation.. The beginning of the Dabeigouan Stage is marked by the first appearance of Nestoria pissovi-Jibeilimnadia ovata in the bottommost conchostracan assemblage zone. The Yushuxia section may serve as an ideal stratotype section of the Dabeigouan Stage. According to the fossil assemblages, sequence of strata, regional stratigraphic correlation and isotopic age data, the age of the Dabeigouan Stage should be Late Jurassic, possibly closer to late Late Jurassic. The paper describes some genera and species of conchostracans.