Abstract: The major elements of detrital rock sample，which collected from Leikoupo formation in No.1 Fenglu well of the west Sichuan depression are analyzed so as to do some research on the content of K and the ratio characteristics of the w(FeO)/w(Fe₂O₃) andw(MnO)/w(FeO+ Fe₂O₃).It is concluded that the content change of the K of Leikoupo formation is positive proportional to the depth，and the content of K is so low that it cannot reach the symbolic line of potassium deposit.As a whole，the ratio value of w(FeO)/w(Fe₂O₃) is less than 1，which indicated that the deposition is under oxidation environment with dry and hot climate conditions.The infinitesimal ratio value of w(MnO)/w(FeO+Fe₂O₃) (less than 1) not only reflects the oxidizing sediment environment and dry and hot climate but also the shallow water environment.Leikoupo formation in west Sichuan depression has a good potassium deposits condition under the instructions of the dry and hot weather condition and secondary tectonic condition of shallow water.The discrimination diagram of w(FeO)-w(Fe₂O₃)-w(MnO) is built based on the research results above.The diagram is divided into three parts，damp cold deep water area，dry hot shallow water area and wet cold shallow water area.According to the research results，the Leikoupo formation belongs to the dry hot shallow water area.

Key words: Major element, Ratio research, Leikoupo formation, Potassium