Lakes located in the monsoon marginal zone in North China are sensitive to climate change. Lake Wulagaigaobi is an enclosed lake in Inner Mongolia of China, which is in the semiarid and sub-humid ecotone on the northeast margin of the Inner Mongolia Plateau. In this paper, a sediment profile of 405 cm deep was chose. The measured data of the sediment in AMS¹⁴C and OSL age revealed that the sediment profile was deposited since 51.9 ka BP. Combined with chronological data and the analyses of sedimentary characteristics, including grain-size distribution, grain-size frequency, grain-size parameters, and trace elements, the evolutionary process and features of the lake environment were reconstructed during the past 50000 years. Results showed that there were four climate periods:51.9-44.1 ka BP (405-343 cm), cold and dry period, a lower lake-level; 44.1-28.5 ka BP (343-130 cm), warm and wet period, the lake-level fluctuated; 28.5-11.38 ka BP (130-35 cm), cold and dry period; 11.38 ka BP-today (35-0 cm), warm and wet period.