Abstract: The "mega-paleolake" in Hetao Basin has great significance for the study of the evolution of the local environment and climate, but its time of the formation and disappearance remains controversial.Based on the HSH drilling data obtained from the southwest coast of Hasuhai lake, the ages of the sediments were determined by AMS ¹⁴C and OSL dating methods.Combined with the zharacteristies of lithology and sedimentary structure, the evolution history of Hasuhai lake was analyzed, and the survival period of Hetao ancient lake was discussed.The results show that the sedimentary environment in the Hasuhai Lake area has undergone the following transformation since the Late Pleistocene.It was a relatively stable lake during 150~70 ka, and transformed into lakeside facies in 70~55 ka due to the decrease of the water level.It turned into swamp in 55~27 ka, and transformed into lakeside facies again during 27~0 ka with the rise of the water level.According to this study, combined with the other research results, it is believed that the "mega-paleolake"in Hetao Basin was formed as early as 150~110 ka.It shrank and even died out during 110~55 ka.After that, although some regions in Hetao Basin were lake or swamp, it was no longer a unified mega-lake.The result is significant for the further study of the environmental changes in Hetao Basin.