Inland lake level changes are extremely sensitive to regional climate and hydrology change,and ancient shorelines are the most direct evidence of lake level changes.Through the field investigation,we found that there were three lake shorelines with elevation 1 026,1 023 m and 1 018 m around the modern Qehan Lake in Inner Mongolia and the OSL dating results of them were 6.830.37,4.260.29 ka BP and 2.420.15 ka BP,respectively,and the paleo lake area were about 270,230 km2 and 120 km2,respectively. The high lake level of Qehan paleo lake stand on 1 023-1 026 m in 6.83-4.26 ka BP,about 8 meters higher than modern,the climate condition then was rather humid.The overall lake fluctuation since Mid- Holocene of Qehan paleo lake was downward and the variation was almost identical to those adjacent lakes inthe arid and semi-arid area.It showed that the Mid-Holocene environmental changes of the Qehan Lake had a profound relationship with the regional and even global climate changing.