Sampling was carried out at Baishui No.1, the largest glacier on Mt. Yulong, China, during the summers of 1999 and 2000, to investigate the spatial variations of oxygen isotopes in the atmosphere-glacier-river system. The results confirm that there is an inverse relation between the oxygen isotopic composition of precipitation and air temperature/precipitation amount. This suggests that a strong “precipitation amount effect” exists in this typical monsoon temperate-glacier region. There are marked differences of the δ18O values of winter-accumulated snow, glacial meltwater, summer precipitation and the glacier-fed river water. Spatial and temporal variations of isotopic composition are controlled by climatic conditions. Isotopic fractionation and differentiation occur during phase changes, snow-to-ice and ice-to-meltwater transformations, and runoff processes. Variations of stable isotopes in glacier runoff can indicate variations of sources of supply, as well as different discharge-related processes. I Sampling was carried out at Baishui No.1, the largest glacier on Mt. Yulong, China, during the summers of 1999 and 2000, to investigate the Spatial variations of oxygen isotopes in the atmosphere-glacier-river system. The results confirm that there is an inverse relation between the oxygen isotopic composition of precipitation and air temperature / precipitation amount. This suggests that a strong “precipitation amount effect” exists in this typical monsoon temperate-glacier region. There are marked differences of the δ18O values ​​of winter -accumulated snow, glacial meltwater, summer precipitation and the glacier-fed river water. Spatial and temporal variations of isotopic compositions are controlled by climatic conditions. Isotopic fractionation and differentiation occur during phase changes, snow-to-ice and ice-to-meltwater transformations, and runoff processes. Variations of stable isotopes in glacier runoff can vary variations of sources of supply, as well as different discharges -related processes. I