Abstract: Based on a newly discovered trilobite fauna of middle Cambrian age, this paper discusses the establishment of the Shilengshui Formation and its geological significance. The Shilengshui Formation is separated from the Gaotai Formation （sensu lato）or the Loushanguan Group and corresponds to the middle-lower part of the Zhangxia Formation and the middle-upper part of the Xuzhuang Formation in North China,with a total thickness of about 177—250m,it is composed of the following three parts. The upper part,24—99m thick,consists of grayish white dolomite, containing a large amount of gypsum,anhydrite and pseudocrystals of halite. It yields trilobites:Manchuriella guizhouensis,M.sp.,Honanaspis sp.and Pro- asaphiscus sp. The middle part,31—137m thick,is composed of grayish white thin-bed- ded dolomite with thin beds of gypsum and pseudocrystal of halite.It yields trilobites.Manchuriella meitanensis,Shilengshuia jiubaensis,S.contracta,S.lata, S.inflexa,Jiubasipis longa,J.brevica,Proasaphiscus intermedius,Protohedinia sp.,Solenoparia sp.,etc. The lower part （?）s marked by thick-bedded dolomite,24—76m thick. This formation is in conformity with its overlying and underlying strata. The sedimentary characteristics of the Shilengshui Formation exhibit salt-forming conditions.Through paleogeographical and paleostructural studies, it is likely to find chlorine salt resources.