The Mboukoumassi region of Congo has tropical rain forest climate, possesses important Cretaceous potash deposits at the western edge of the African continent, and hence belongs to the typical rift potassium basin. Mineralogical studies show that the main types of evaporite minerals are chloride minerals comprising halite, carnallite, kalitite, brucite and spillite, sulfate minerals comprising gypsum, anhydrite and some other minerals. The sequence of evaporite mineral deposition is in order of gypsum, anhydrite (most cycles are missing) → stone salt → carnallite → potassium salt (secondary) → spillstone or magnesite. According to the characteristics of evaporite mineral deposition and the analysis of trace elements, it is shown that, in the Cretaceous period, the Mboukoumassi area was in a long-term high temperature and dry environment, which was conducive to the evaporation and concentration of brine and the formation of salt mineral deposition.