Abstract: Two cores of samples from Bangong Co and Sumxi Co and lacustrine sedimentary samples from one exposure near the Hongshan lake were collected. In order to obtain information about the environmental changes in the West Kunlun and Karakorum Mountains region since the late Pleistocene. detail analyses of ostracods have been carried out. On the basis of the distribution of ostracod fossils and their palaeoecological characters.it can be considered that a cold climate occurred beween 17 000 and 12 000 a BP, especially in the period 17 000-15 000 aBP. The runoff into the lake might slightly increase which infers a little warm up after 15 000 aBP. Assemblage character of ostracods and sedimentary features shows that the lakes in this area were slightly extended during the time of 12 500-12 000 aBP. No ostracod has been found in the strata in 11 500-10 000 aBP. This may correspond to the cooling event of Younger Dryas. When the Younger Dryas ended. the temperature rose rapidly, fine hydrological conditions for the development of ostracods appeared during the period about 10 000 aBP and 7 500-6 000 aBP which coincided with the rise of lake level and a warm-humid climate. Clinatic deterioration occurred since 6 000-5 500 aBP The water in the Bangong Co became slightly saline after 5 500 aBP. 

Key words: Qinghai-Xizang Plateau, Ostracod Fauna, Last Glaciation, Post Glaciation, environmental variation