The Linxi Formation is a improtent sedimentary strata of the Permaian in Great Hinggan Mountains,and the degree of study is also directly affect the reaserch about close of the paleo- Asian ocean,the joint of two plates,transformation of depositional environment and other major geological problems.The research area is mainly located in the central part of Great Hinggan Mountains,based on field investigation,the marine oncolitic limestone of the Upper Permian Linxi Formation has been found for the first time in Bayanwulan area,Zhalaite Banner,Inner Mongolia.Methods: Base on the study methods of petrology,geochemistry, paleontology,and also element geochemistry.Results: It confirms that the oncolitic limestone grow out of the warm and turbulent shoal environment of edge of carbonate platform,which has obvious marine facies characteristics,and found the combination of palaeanodonta sp.—palaeomutela sp.fossils,which have obvious characteristics of continental deposition in lower—middle part of the Linxi Formation.This shows that this area existed the sedimentary environment of marine facies or paralic facies in early Late Permian,with the environment changed,the Linxi Formation turned to the sedimentary environment of river and lucustrine facies gradually.Conclusions:This discovery not only improved the structure of the Linxi Formation in the Xingmeng area(Great Hinggan—Inner Mongolia area),but also provides reliable datas of the research on the sedimentary evolution of the Xingmeng Trough during the transitional period from late Paleozoic to Mesozoic.