The Kunteyi area in the western Qaidam Basin is an important potassium-rich mineral resource belt in China, yet research on the genetic mechanism and geochemical characteristics of its deep sand-gravel pore brine remains lacking. Taking the deep sand-gravel pore brine in the Lower Pleistocene brine-bearing reservoirs at depths greater than 220 m from three boreholes in this area as the research object, this study conducted investigations via hydrochemical analysis, hydrogen and oxygen isotope testing, and ionic characteristic coefficient analysis. The results show that the brine is a high-salinity confined Na-Cl type brine with an average salinity of 287.39 g/L. The contents of K? and Na? meet the industrial evaluation criteria, with strong water yield property and continuous, stable spatial distribution. Ionic characteristic coefficients indicate that the brine is of the evaporation residue-halite leaching type, where potassium salts are in the stage of dissolution and concentration, and the formation has poor sealing performance. Hydrogen and oxygen isotopes reveal that the brine originates from meteoric water and undergoes intense evaporation and concentration, with its fitting curve being consistent with the characteristics of regional surface lake brine. The mineralization process is characterized by two stages: in the early stage, concentrated paleo-brine formed under the coupling of the "high mountain-deep basin" geomorphic pattern and arid climate; in the late stage, tectonic movements drove fluids to leach paleo-salt layers, and ore-forming materials accumulated in the pores of sand-gravel layers to form mineral deposits. This study confirms that the Kunteyi area is an important prospective area for liquid potassium salt deposits, which can provide a theoretical basis for subsequent exploration work.