During 2009-2010, surface water samples from 34 Tibetan lakes were collected and measured for major ions. The distribution pattern of ionic concentrations and its response to regional climatic change were investigated. Results revealed a large range of major ionic concentrations as well as other water parameters for the lakes. Most lakes showed higher ionic concentrations than lakes in other regions of China and even the world. Most of the lakes' water types were found to be Na(K)-Cl with a few as Ca(Mg)-SO₄. Due to the effect of evapoconcentration, water types of Tibetan lakes showed a gradient variation in the order of Ca(Na)-HCO₃Na(K)-SO₄Na(K)-Cl along the southeast-northwest transect. Compared with the pre-1990s data, the concentrations of major ions in the majority of the lakes decreased and the water type of several lakes also changed. The variation of major ions and water types of Tibetan lakes indicated an obvious response in lake water chemistry to the regional climatic changes over decades.