The Qaidam Basin represents an important provenance for potassium salt in China and in the world. So far, studies have mostly focused on potassium salt in shallow subsurface salt lakes, whereas little has been reported about potassium salt in deep clastic pores. In the present study, the spatial-temporal evolutions involved in the metallogenesis of potassium salt in the Qaidam Basin are summarized within the context of the Kunteyi Sag as an example. A "double-layered potassium salt" model consisting of intercrystalline brine in the Q_p2-h salt-lake facies chemical salt crystal fissures underlain by the Q_p1 alluvial-proluvial gravel pore brine is established after investigating the local geology, paleo-environment, and brine reservoir distribution in the study area. The genesis of this "double-layered potassium salt" model and the internal connections between the overlying and underlying brine layers are explored by comparing the ionic contents in these layers through mathematical and geochemical approaches such as cluster analysis, characteristic coefficient, piper trilinear nomograph, and hydrogen and oxygen isotopes. The results indicate that within the Qaidam Basin, the brine in the "double-layered potassium salt" unexceptionally comprises salt rock lixiviation water from a continental sedimentary background. The overlying intercrystalline brine suggests more of salt rock dissolution, although lixiviation may have also played a role; the underlying gravel pore brine points more toward rock salt dissolution. The overlying intercrystalline brine seems to originate from the deep evolution of the underlying gravel pore brine, whereas the underlying gravel pore brine appears to be successive from the deep paleo-salt rock layers and the overlying intercrystalline layer. The oilfield water in the Neogene anticlinal structures surrounding the Kunteyi Sag also shows a close genetic connection with the "double-layered potassium salt" brine.