Abstract: Taohaiyingzi in Aru-Horqin Qi is one of the typical areas where Late Permian Linxi Formation is well developed. Linxi Formation is lithologically dominated by the assemblage of black, dark gray and celadon sandstone and slate, with rich non-marine fossils in the upper part. The mudstone samples from Linxi Formation in Taohaiyingzi profile and LD2 well are analyzed for constant elements and trace elements with geochemical method. It is found that the Linxi Formation is generally characterized by high silicon, aluminum and calcium, and low phosphorus and manganese. Based on the fossil assemblage and preservation condition, it is believed that the Linxi Formation in this area was formed in the sedimentary environment of salt-fresh water, with a desalting process. The bottom of the formation is in the sedimentary environment of sea-land interaction; while the upper part is the fresh water lake of continental facies.