The evolution of inland lakes in Tibet Plateau provides important information about past climatic change. The retreating processes of lake shorelines can be used to infer lake evolutions forced either by tectonic events or climatic change. Identification of the past shorelines is very important in the recognition of climate and tectonic events. In this paper，we focused on studying the lake of Siling Co，which is the second largest inland lake in Tibet Plateau. Our field investigations indicate that wellpreserved shorelines can be found in the northeastern bank of this lake. By using singlealiquot regenerativedose(SAR)protocol method，we yielded three ages for the past shorelines，which imply that stepwise retreating of the lake occurring at 12.2 ka， 6.3 ka and 2.3 ka，respectively.