During the deposition of salt lake, potassium and magnesium salt began to crystallize out at the middle late stage of salt mineral deposition. Therefore, studying the geochemical characteristic of halite obtains not only the source information of salt minerals but also ancient brine concentration and the trends of potassium enrichment regularity of the ancient salt lake. In the Paleogene Shashi Formation of Jiangling depression and other salt system, potassium rich brines were found. The trace amount of sylvite and syngenite were found in salt rock of the formation of the Paleogene Shashi in salt mine and potash exploratory drill well. It shows that the area may have potential to exploit sylvite. Based on research of evaporite rocks features of SK3 well and vertical variation regularity of such coefficients of K, Mg, Cl, Br ions and Br×103/Cl, it reveals the evolution of salt lake and the trend of potassium enrichment, and furtherly reveals potassium enrichment degrees of salt lake.