The oilfield brines with a great quantity of reserves exist in the PaleogeneNeogene in some anticlines of the western Qaidam Basin. They are expected to be the resources to sustain  the Quaternary salt lake brines. By the analyses of the oilfield brines samples collected from the  boreholes in the typical tectonic areas including Xiaoliangshan, Youquanzi, Kaitemilike, Youdunzi, and Youshashan and the saline lake brine samples, and intercrystal brine samples on earth, the hydrochemistry characteristics and resource distribution are discussed. Compared with the evaporate curves of the marine water and the Qinghai Lake water, the chemical evolution of the oilfield brines is analyzed. The results indicate that the resources of K, B,Li are much higher than the industrial grade. Br and Sr also reach the industrial grade. Thus the exploration and utilization prospect of oilfield brines is very good. The planar distribution of oilfield brines is characterized by most enriching in the central Nanyishan anticline and reducing toward the north and the south. Vertically, the oilfield brines are more likely to enrich in the deep interval than in the shallow interval intercrystal brines and the lacustrine water. The chemical evolution of oilfield brines is dominated by waterrock reaction, mixing, evaporation and condensation of deep water and salt rock dissolution. These processes provide good geochemical conditions for the brines evolution and accumulation. 