Abstract: Some freshwater Molluscs shells are collected from modern freshwater lake and Quternary stratum in China,in which climate and environment have been known in detail. The oxygen istopic composition of freshwater Molluscs shells are analysed for discussing relationship between the oxygen isotopic composition of shell and terrestrial climate and enviroment,and it used to reconstruct the past climatic chang. In this paper, the whole shell sample are analysed for discussing relationship between shell δ¹⁸O_PDB and annual mean temperature and δ¹⁸O_SMOW of lake water. The results show that: Molluscs shell in freshwater Lake are rich in O.δ¹⁸ O_PDB5‰, in comparision with marine Molluscs. The δ¹⁸O_PDB value of Molluscs shells which lived in same area are similar; but that which lived in different area are different. During moisture climate, δ¹⁸O_PDB value of shells range from -5. 1～-10. 2‰. The shell is richer in O, with of gtadually increasing. δ¹⁸O_PDB of shell is related to δ¹⁸O_P(SMOW) of annual mean precipitation. The linear equation is δ¹⁸O_p(SMOW) = 1. 07δ¹⁸OS -0. 58. During dry climate. the oxygen isotopic composition of shell is rich in O. All these indicate that the oxygen isotopic composition of whole shell is inherited from that of Lake water. The freshwater Molluscs shell fossils from Quternary stratum is also rich in δ¹⁸O, is similar ro modern Molluscs shell, The δ¹⁸O_PDB of shell range from - 6. 2- 14. 6‰. For example, in Kunming area.the δ¹⁸O_PDB value of shell fossil from different age is different. The δ¹⁸O offset value is up to 7‰. During moisture and warm climate, the Molluses shell fossils is rich in O. in comparision with modern shell in some area. Showing that the global temperature is high,and the precipitation and melt of the snow is on the increase, this water is rich in O6 and flowed to Lake, where the Molluscs Lived in, thus the molluscs is also rich in O1 During dry and cool climate, the Molluscs shell fossils is show that, the global temperature is low, ind the pricipita-tion is decrease, but the evaporation is strong, so that the light isotopic composition are esccped thus, water body is rich in O, and concentrated in lake, where the Molluscs lived in, thus the Molluscs is also rich in O. In all above,the δ¹⁸O of fossil shell from lake. Sensetively recorded past wet and terrestrial climate chang.