Abstract: Previous researches on the Upper Permian Linxi Formation in Linxi County and Taohaiyingzi Formation in Jalaid Banner show that the main fossils are freshwater bivalves and plant fossils. Except for Taohaiyingzi Formation, conchostracan fossils had never been discovered in this area. In this study, the conchostracan fossils were discovered firstly in the upper part of the Linxi Formation in Guandi section of eastern Linxi County, Inner Mongolia, which are preliminarily identified as Huanghestheria linxiensis Niu(sp. nov)., Cyclotunguzites cf. gazimuri Novojilov, and Sphaerorthothemos cf. cellulatus(Lutkevich) respectively. Therefore, the conchostracan fossils discovery in Linxi Formation provides the reliable fossil evidence for the determination of the age of Linxi Formation as well as for stratigraphic correlation and palaeogeographic reconstruction. This achievement has important stratigraphic and palaeogeographicy tectonic significance.