The section of the 10mdeep 37/ZK7 hole in Nyêr Co paleolake, western Tibet, contains abundant aquatic microfossils such as ostracods and charophytes. Of these, the ostracods are the most abundant group but have a low diversity. The ostracods that occur frequently and have a high abundance are Leucocythere mirabilis Kaufmann and Limnocythere dubiosa Daday, while others including Limnocytherellina, Eucypris and Candona that are of much less abundance. Charophytes occur in many horizons, but their oogonia are poorly preserved and what have been preserved are mostly the fragments of vegetal bodies and the membranes of ova. According to the analyses of the ecoenvironment of ostracods, combined with the Useries dating and sedimentary data of the section, as well as the relevant geochemical background values, the paleoenvironmental changes of the Nyêr Co Paleolake at 20000—2000 a BP were largely as follows. ① Around 20000 a BP, the lake water was relatively deep, the water temperature relatively low and the water quality  slightly salty. The climate was relatively coolwet and then became warmwet. ② During 18700—18100 a BP, the lake water had a high evaporation quantity, so that the lake area shrank and the lake became shallow gradually. The salinity increased and the climate was slightly warmdry. ③ During 18100—11800 a BP, the climate was coldwet. The lake water was relatively deep, the water temperature slightly low and the water quality relatively tasteless.However, there were several climatic fluctuations and the lake depth and hydrochemical properties changed with climatic oscillations in this period, suggesting that the climate in the lake district was characterized by a repeated alternation of relatively coldwet and coolslightly wet and became coolslightly dry at the late stage. ④ During 11800—10000 a BP,  the climate became slightly warmwet(11800—11000 a BP) and then became colddry(11000—10000 a BP). The ecoenvironment of the lake deteriorated and the number of ostracods decreased abruptly, which should be the response to the global Dryas event in the study area. ⑤ At 10000 a BP in the Holocene, the climate was slightly warmwet(10000—8700 aBPand 7000—4800 aBP), with slightly a coldwet climate (8700—7000 aBP); during 4800—3000 a BP, the climate became alternately slightly warmdry(4800—4600, 4400—4300 and 3800—3000 a BP) and slightly coldwet(4600—4400 and 4300—3800 a BP); and during 3000—2100 a BP, the climate was mainly colddry and by then the lakes had been nearly driedup.